Add conservative inline script cache clearing (preview)

[StellaHuang95]

Fork-review PR for a deliberately conservative, default-off feedback rollout.

This replaces the earlier comprehensive lifecycle implementation with a small preview-specific cache clear. It intentionally omits project migration, PID probing, and general lock recovery.

What this preview does

Adds Python: Clear Script Environment Cache (python-envs.clearInlineScriptCache) without changing the existing broad python-envs.clearCache command.

The preview command:

1. is hidden/disabled unless python-envs.inlineScripts.enabled is on;
2. waits for the inline manager's bounded registration readiness;
3. requires modal confirmation;
4. targets only the physically verified <globalStorage>/script-envs-v1 directory;
5. rejects symlink/junction or redirected roots;
6. coordinates create and clear across windows with a short root-maintenance-lock to entry-lock handoff;
7. refuses active, orphaned, malformed, or unverifiable entry locks;
8. permits explicit deletion of locks carrying the exact retained marker created after package-install cancellation;
9. clears PR7 Memento associations and in-memory association/validation state;
10. prevents pending rehydration from repopulating cleared state and emits removal events for known affected scripts.

Root-lock and owner-lock errors include the exact path and conservative manual-recovery guidance. New root-lock release failures are fatal; existing per-entry release behavior is unchanged.

Intentional limitations

• no pythonProjects[] cleanup or migration;
• no TTL eviction;
• no PID/liveness probing or stale-owner recovery;
• no generalized lockfile API changes;
• no routing, setup UI, telemetry, or status behavior;
• a crash-abandoned root/owner lock may require carefully removing the reported lock path after restart.

Size

• production: 417 additions, 23 deletions across six production files
• tests/wiring: focused command, locking, state, event, and registration coverage

Validation

• TypeScript test compilation and extension compilation
• ESLint
• focused cache/command suite: 37+ passing across final iterations
• smoke registration checks
• eight manual review passes; no significant findings remain

[StellaHuang95]

Closing this PR in favor of a clean-history replacement with the same current reviewed file changes.

[StellaHuang95]

Superseded by clean-history replacement #8.