Security: Phase 3 Rust advisory umbrella

[saagar210]

Phase 3 umbrella tracking issue for temporary Rust advisory waivers in scripts/security/run-cargo-audit.sh.

Scope:

• Track mitigation ownership for all currently ignored RUSTSEC advisories.
• Enforce review date governance (current review target: 2026-03-01).
• Close or re-time-box each waiver with explicit owner and rationale.

Child issues:

• Security: Mitigate GTK3 advisory chain from Tauri Linux runtime #12 GTK3/Tauri Linux runtime advisory chain
• Security: Mitigate tauri-utils advisory chain (urlpattern/unic/fxhash) #13 tauri-utils advisory chain (urlpattern/unic* + fxhash)
• Security: Mitigate lancedb advisory chain (paste) #14 Lance/DataFusion advisory chain (paste)
• Security: Mitigate tantivy/lru unsound advisory chain #15 Tantivy/Lance advisory chain (lru)

Exit criteria:

• Remove waiver where feasible via upgrades/feature-pruning.
• For unresolved items, document explicit risk acceptance with owner, issue, and next review date.