Tasks: bound version-stats default reads

1. OpenSpec

• 1.1 Add an OpenSpec change explaining the bounded-default advisory model.
• 1.2 Validate the change with openspec validate bound-version-stats-default-read --strict.

2. Console hot path

• 2.1 Remove the live version-stats fetch from /dashboard/records.
• 2.2 Keep demo-only churn advisory fixtures available for screenshots.
• 2.3 Update the page-performance invariant for the current shell component.

3. Server default route

• 3.1 Make unfiltered version-stats always use the bounded projection path.
• 3.2 Do not include dirty projection rows in the unfiltered ground-truth candidate set.
• 3.3 Preserve scoped ground-truth diagnostics for explicit filters.

4. Tests

• 4.1 Update record-version-stats tests for bounded dirty-default behavior.
• 4.2 Add/keep a scoped diagnostic test proving exact ground truth remains available.
• 4.3 Run the Sources page performance invariant test.
• 4.4 Run the version-stats test suite.

5. Validation

• 5.1 Run openspec validate bound-version-stats-default-read --strict.
• 5.2 Run openspec validate --all --strict.
• 5.3 Run relevant type/check commands or document why they were not run.