Add controller case file template

Author: mdheller

docs/controller-sovereignty/case-file-template.md

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+# Controller Case File Template
+
+Use this template for redacted controller-sovereignty evidence. Repository artifacts should contain summaries, not private device records.
+
+## Summary
+
+- Case ID: `<case-id>`
+- Date range: `<start> to <end>`
+- Machine class: `<redacted>`
+- OS family/build: `<OS family and build>`
+- Primary finding: `<one sentence>`
+
+## Controller
+
+- Controller name: `<Spotlight / Photos / APFS / CoreWiFi / Network Extension / updater / other>`
+- Owner: `<first-party | third-party | user | unknown>`
+- Representative services:
+  - `<service name>`
+- Resource coalition: `<if known>`
+
+## Trigger model
+
+- Foreground user action observed: `<yes | no | unknown>`
+- Background scheduler observed: `<yes | no | unknown>`
+- Network trigger observed: `<yes | no | unknown>`
+- Filesystem trigger observed: `<yes | no | unknown>`
+- Cloud/sync trigger observed: `<yes | no | unknown>`
+
+## Observed behavior
+
+Describe what the controller did in plain language.
+
+Example:
+
+> Metadata controller compacted index payloads and dirtied several GB of file-backed memory while running non-frontmost background work.
+
+## Resource impact
+
+- CPU: `<duration / average / peak if available>`
+- Disk writes: `<MB/GB and duration if available>`
+- Memory: `<RSS/footprint if available>`
+- Network: `<interfaces, tunnels, or traffic-class evidence if available>`
+- Power state: `<AC / battery / idle / active>`
+- Platform action: `<none / managed / unknown>`
+
+## Evidence summary
+
+| Evidence | Sanitized value |
+|---|---|
+| Event type | `<disk writes / cpu usage / telemetry loop / network policy / other>` |
+| Command | `<process name>` |
+| Time window | `<redacted or normalized>` |
+| Stack family | `<Spotlight compaction / Photos database rewrite / APFS traversal / Wi-Fi telemetry>` |
+| User activity | `<active / idle / unknown>` |
+| Power source | `<AC / battery / unknown>` |
+
+## User-control gap
+
+- Was the behavior visible in the UI?
+- Could the user defer it?
+- Could the user budget it?
+- Could the user audit what file class, interface, or service was touched?
+- Could the user revise the capability safely?
+
+## Classification
+
+- Evidence confidence: `<low / medium / high>`
+- Resource impact: `<low / medium / high>`
+- User-control gap: `<low / medium / high>`
+- Recommended design response: `<observe / budget / governed profile / redesign>`
+
+## SourceOS design requirement
+
+Translate the case into a requirement.
+
+Example:
+
+> A metadata indexer that exceeds a configured write budget must emit a ControllerBudgetExceeded event with file-class attribution and user-visible policy state.