feat(render): gauge strip and checked line in the default inspect view

[alexshapalov]

What changes

The default `pgbot inspect` view gets a four-row gauge strip right under the header, and the GOOD bullet list becomes a compact `checked · …` line. Score, CRITICAL/WARNING/NOTE bullets and the footer stay. `--full`, `--json`, MCP, SARIF and the HTML report are untouched.

```
connected · prod-eu-1 · postgres 16.3 · read-only · 6h window

cache hit [████████████████████] 99.2% ok
lock wait [████████████░░░░░░░░] 61.0% query 4f2a
rollbacks [██░░░░░░░░░░░░░░░░░░] 12.0% watch
idle idx [██████░░░░░░░░░░░░░░] 43.0 GiB review

checked · queries · vacuum · replication · checkpoints
· connections · settings · deadlocks

Database health: 82/100
```

The four gauges

Each row is a label, a 20-cell bar (rounded to the nearest cell, one-cell minimum for any non-zero value), a value, and a status word driven by the finding that grades the same signal — never a threshold of its own.

• cache hit — sampled ratio; `ok`, or `low` when `low_cache_hit` fired. Under the block threshold the row reads `— thin sample`, dim.
• lock wait — the Lock bucket's share of sampled active time from the wait profile. `ok` with no blocked sessions; with blocked sessions it names the culprit (`query <4 hex of query_id>`, highest lock share), falling back to `N blocked`. Without a wait profile the value is `—` and only the status shows.
• rollbacks — rollback ratio; `ok` or `watch` when `high_rollback_ratio` fired. Nil ratio → not measurable.
• idle idx — summed size of zero-scan indexes; fill is that size over database size (the model has no total-index-bytes, and db size is the honest stand-in). `ok` or `review` when `unused_indexes` fired. Cold window → dim `window < 15m`.

The checked line

Subsystems that were collected and produced no finding, fixed order: queries, indexes, vacuum, replication, checkpoints, connections, settings, wraparound, deadlocks. A subsystem whose gauge is already orange/red is left out so the line never contradicts the strip. Wraps whole items with an eight-space hanging indent. Skipped under the schema profile, like GOOD was.

Files

• `internal/render/gauges.go` — new: the four gauges, the strip, the checked list and its renderer.
• `internal/render/dashboard.go` — calls them before the score, drops the GOOD block and `buildGood`.
• `internal/render/gauges_test.go` — fill rounding, every not-measurable state, culprit selection (incl. negative query ids), exact no-color layout, 80-column width, checked ordering/exclusion/wrapping, schema skip.
• `terminal_test.go` GOOD expectations updated; grouped golden regenerated (bullets unchanged).
• README quickstart sample, CHANGELOG.