fix(security): resolve Dependabot #5 (lru unsound) + Code Scanning #7 (actions expr-injection)

[hyperpolymath]

Dependabot alert #5 — lru 0.12.5 unsound iterator (RUSTSEC-2026-0002 / GHSA-rhfx-m35p-ff5j)

Pulled in transitively via ratatui 0.29 → lru ^0.12. Bumped ratatui to 0.30 (which dropped its lru dependency entirely) and crossterm to 0.29 to satisfy the new lower bound. The lockfile now resolves to lru 0.16.4 (≥ patched 0.16.3) via an unrelated transitive path. coord-tui's ratatui API surface is unchanged in 0.30; release build is green and cargo audit reports 0 vulns / 0 warnings.

Confirmed by the post-push remote notice: the default branch reports "1 vulnerability (1 low)" pointing at alert #5 — matches the unsound-tier lru advisory.

Code Scanning alert #7 — best-guess: actions/expression-injection in instant-sync.yml

⚠️ Note: I couldn't read alert #7 directly — the GitHub MCP server available to me doesn't expose the code-scanning alerts endpoint, and WebFetch 404s on the unauthenticated URL. The user opted into a broad scan rather than pasting the alert.

The only ${{ github.event.* }} value interpolated directly into a run: shell line in this repo is github.event.repository.name at instant-sync.yml:33 — the canonical CodeQL actions/expression-injection sink. Fixed by:

• Confirm step: bind to env: REPO_NAME and reference $REPO_NAME from the shell (documented mitigation).
• Trigger Propagation client-payload: wrap each interpolation in toJSON(...) so the JSON template remains well-formed even if a value contains " / \n.

If alert #7 was actually pointing somewhere else, please drop the rule ID / file:line into a review comment and I'll redirect the fix.

Test plan

• cargo build --release in coord-tui/ — green
• cargo audit in coord-tui/ — 0 vulns, 0 warnings
• CodeQL re-scan on this branch confirms alert Add node operator tray app and browser extension #7 closed (will know after CI)
• Dependabot re-scan confirms alert Remove 11 unnecessary CI workflows #5 closed

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