Add inline script environment lifecycle telemetry (PEP 723 PR 15/16) (#1723)

> Part of #1602 (PEP 723 inline script env support). Design doc: #1601.
>
> Builds on the merged creation, uv-fallback, and persistence work in
#1656, #1696, and #1697. This branch is rebased on current `main`.

### Roadmap context

This is **PR 15 of 16** in the PEP 723 inline-script roadmap. It adds
the remaining lifecycle telemetry for the internal manager without
changing routing, creation, or cache policy.

| Phase 5: Lifecycle and polish | PR | Status |
|---|---|---|
| | PR 13: clear inline-script cache | separate |
| | PR 14: opportunistic TTL eviction | follow-up |
| | **PR 15: lifecycle telemetry** | **this PR** |
| | PR 16: status-bar decision | resolved; no code PR |

### Why this PR

The manager can create, reuse, and persist inline-script environments,
including consent-gated uv/Python fallback, but those lifecycle outcomes
are not observable as a coherent feature funnel.

This PR adds low-cardinality telemetry that answers:

- whether setup built a new environment or reused a validated cache
entry;
- how long actual environment construction took;
- how many normalized dependencies were involved; and
- which stable failure category prevented setup.

The instrumentation is deliberately attached to the underlying coalesced
operation rather than every caller, and it excludes
script/package/interpreter content.

### What this PR does

**Adds three typed lifecycle events**

- `inlineScript.envCreated`
- `inlineScript.envReuseHit`
- `inlineScript.envError`

The telemetry constants and GDPR declarations use typed event/property
mappings so call sites cannot send undeclared fields.

**Reports verified creation only**

- Emits `envCreated` only after environment creation succeeds,
ownership/version validation passes, and `.meta.json` is persisted.
- Measures the actual build/rebuild interval rather than lock waiting or
cache inspection.
- Reports normalized, deduplicated dependency count rather than raw
dependency values.
- Emits one creation event for the underlying coalesced operation, even
when multiple callers await it.

**Reports validated cache reuse only**

- Emits `envReuseHit` only after sidecar, interpreter, ownership, and
compatibility checks complete successfully.
- Does not report a hit for uncertain, stale, malformed, or partially
validated entries.
- Preserves the existing cache reuse and `lastUsedAt` behavior.

**Classifies lifecycle failures without leaking details**

`envError` uses stable low-cardinality categories for outcomes such as:

- environment discovery failure;
- no compatible Python;
- declined compatible-Python installation;
- uv/Python installation failure;
- general setup, cache-validation, or metadata-persistence failure;
- package-install cancellation;
- cache-lock timeout; and
- retained, orphaned, or otherwise unavailable lock state.

Errors remain logged through the existing paths; telemetry sends no
exception text.

**Preserves uv consent and compatibility behavior**

- Adds detailed internal uv lookup/install result types so the manager
can distinguish `available`, `declined`, `failed`, and `installed`
outcomes.
- Keeps existing compatibility wrappers for callers that only need
boolean/path results.
- Does not change prompt text, consent requirements, install selectors,
restart-required behavior, or uv's existing telemetry.

**Keeps event emission coalesced and deterministic**

- Same-key concurrent creation/reuse callers receive one lifecycle
result for the shared operation.
- Cache inspection, lock acquisition, fallback selection, cancellation,
and cleanup retain their existing control flow.
- Non-applicable `create()` calls and pre-validation exits do not emit
success-shaped lifecycle events.

### Event payloads and privacy

| Event | Data |
|---|---|
| `inlineScript.envCreated` | build duration; normalized dependency
count |
| `inlineScript.envReuseHit` | normalized dependency count |
| `inlineScript.envError` | stable failure category |

The events send no:

- script URI or filesystem path;
- requirement or dependency value;
- package name;
- Python/interpreter version;
- cache key;
- prompt text; or
- exception/error-message content.

Script-controlled metadata therefore cannot create unbounded telemetry
dimensions.

### Lifecycle examples

```text
validated cache hit
→ emit one inlineScript.envReuseHit
```

```text
cache miss or stale entry
→ start build timer
→ build + install dependencies
→ validate ownership/version
→ persist sidecar
→ emit one inlineScript.envCreated
```

```text
no compatible Python
→ user dismisses consent prompt
→ emit one inlineScript.envError with the declined category
```

### Tests

Coverage includes:

- creation emitted only after verified sidecar persistence;
- validated reuse and rebuild behavior;
- one event for concurrent/coalesced callers;
- duration boundaries excluding lock wait/cache inspection;
- normalized/deduplicated dependency counts;
- discovery, compatibility, consent, installation, cancellation, setup,
and lock categories;
- no lifecycle telemetry for non-applicable calls;
- direct detailed uv results for available, declined, failed, and
installed outcomes; and
- preservation of existing uv wrapper behavior.

Validation on the rebased branch:

- `npm run compile-tests`
- `npm run compile`
- `npm run lint`
- focused lifecycle/detailed-uv suites: 39 passing

The full Windows unit run reaches 1612 passing and 5 pending; the
existing concurrent `writeMetaJson` rename test can still intermittently
fail with `EPERM` on Windows. That writer is unchanged by this PR and
the same failure is reproducible on `main`.

### Performance

- No activation work, scan, timer, watcher, or new filesystem operation
is introduced.
- Instrumentation performs constant-size event construction around
operations that already occur.
- Coalesced setup emits once rather than once per waiter.
- No user-controlled strings are normalized or transmitted beyond the
dependency count already needed for the cache operation.

### User impact

**No default-path user impact.** The inline manager remains behind the
undeclared, default-off `python-envs.inlineScripts.enabled` flag.

When the internal flag is manually enabled, prompts, environment
creation/reuse, cancellation, error propagation, and cache behavior
remain unchanged. This PR only records privacy-safe lifecycle outcomes.

### Scope and follow-up

This PR intentionally does **not** implement:

- script detection or automatic routing;
- activation-time cache discovery;
- project registration or user-facing setup UX;
- cache clearing or TTL eviction; or
- status-bar behavior.

The telemetry is ready for those later entry points to consume once the
feature is intentionally exposed.

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 3cb82ae9-7424-40a4-9156-8c54ac6e0895
Copilot-Session: 6b12d843-8011-4bfc-9ba9-f75761eadee2

Author: StellaHuang95

src/common/telemetry/constants.ts

@@ -221,6 +221,29 @@ export enum EventNames {
      * - dependencyCount: number (number of entries in the `dependencies` list)
      */
     INLINE_SCRIPT_DETECTED = 'inlineScript.detected',
+    /**
+     * Telemetry event fired when inline-script environment creation completes
+     * successfully with a newly-built cache entry that passed verification and
+     * metadata persistence.
+     * Measures:
+     * - duration: number (ms spent in the underlying create/rebuild operation)
+     * - dependencyCount: number (normalized dependency count in the cache key)
+     */
+    INLINE_SCRIPT_ENV_CREATED = 'inlineScript.envCreated',
+    /**
+     * Telemetry event fired when inline-script environment creation validates
+     * and reuses an existing cache entry without rebuilding it.
+     * Measures:
+     * - dependencyCount: number (normalized dependency count in the cache key)
+     */
+    INLINE_SCRIPT_ENV_REUSE_HIT = 'inlineScript.envReuseHit',
+    /**
+     * Telemetry event fired when inline-script environment creation cannot
+     * complete.
+     * Properties:
+     * - category: stable low-cardinality failure category
+     */
+    INLINE_SCRIPT_ENV_ERROR = 'inlineScript.envError',
     /**
      * Telemetry event fired once per session, per URI, the first time a `.py`
      * file that previously raised an `inlineScript.detected` event receives a
@@ -232,6 +255,16 @@ export enum EventNames {
     INLINE_SCRIPT_EDITED = 'inlineScript.edited',
 }
 
+export type InlineScriptEnvErrorCategory =
+    | 'compatible-python-declined'
+    | 'discovery-failure'
+    | 'no-compatible-python'
+    | 'package-install-cancelled'
+    | 'install-failure'
+    | 'setup-failure'
+    | 'lock-timeout'
+    | 'lock-unavailable';
+
 // Map all events to their properties
 export interface IEventNamePropertyMapping {
     /* __GDPR__
@@ -695,6 +728,36 @@ export interface IEventNamePropertyMapping {
         errorType?: string;
     };
 
+    /* __GDPR__
+        "inlineScript.envCreated": {
+            "dependencyCount": { "classification": "SystemMetaData", "purpose": "FeatureInsight", "isMeasurement": true, "owner": "StellaHuang95" },
+            "<duration>": { "classification": "SystemMetaData", "purpose": "FeatureInsight", "isMeasurement": true, "owner": "StellaHuang95" }
+        }
+    */
+    [EventNames.INLINE_SCRIPT_ENV_CREATED]: {
+        // Goes through the measures payload (numeric); listed here for GDPR only.
+        dependencyCount?: number;
+    };
+
+    /* __GDPR__
+        "inlineScript.envReuseHit": {
+            "dependencyCount": { "classification": "SystemMetaData", "purpose": "FeatureInsight", "isMeasurement": true, "owner": "StellaHuang95" }
+        }
+    */
+    [EventNames.INLINE_SCRIPT_ENV_REUSE_HIT]: {
+        // Goes through the measures payload (numeric); listed here for GDPR only.
+        dependencyCount?: number;
+    };
+
+    /* __GDPR__
+        "inlineScript.envError": {
+            "category": { "classification": "SystemMetaData", "purpose": "FeatureInsight", "owner": "StellaHuang95" }
+        }
+    */
+    [EventNames.INLINE_SCRIPT_ENV_ERROR]: {
+        category: InlineScriptEnvErrorCategory;
+    };
+
     /* __GDPR__
         "inlineScript.detected": {
             "trigger": { "classification": "SystemMetaData", "purpose": "FeatureInsight", "owner": "StellaHuang95" },