ci(labeler): add tui/daemon/sidecar auto-label rules

[kovtcharov-amd]

Why this matters

The terminal-hub / sidecar architecture work (milestone #45) added new code surfaces the auto-labeler didn't know about, so PRs touching the Go TUI, the daemon supervisor, or the agent sidecar contract landed unlabelled and had to be triaged by hand. This teaches actions/labeler about those paths and introduces the matching tui / daemon / sidecar repo labels (already created), so future PRs in these areas self-label.

Test plan

• labeler.yml parses as valid YAML and every referenced label exists as a repo label.
• A PR touching tui/** (or .github/workflows/build_tui.yml) receives the tui label.
• A PR touching src/gaia/daemon/** receives the daemon label.
• A PR touching src/gaia/daemon/sidecars/** or hub/agents/*/python/packaging/** receives the sidecar label.

No change to auto-label.yml — it's generic (actions/labeler@v6, no per-label config), so the new rules take effect on next PR event.

[github-actions]

Verdict: Approve ✅

Adds three auto-label rules (tui, daemon, sidecar) so PRs touching the terminal-hub/sidecar surfaces self-label instead of needing manual triage. All the referenced paths (tui/, src/gaia/daemon/, src/gaia/daemon/sidecars/, build_tui.yml, hub/agents/*/python/packaging/) exist today, the YAML parses cleanly, and the new blocks mirror the file's existing changed-files / any-glob-to-any-file structure. No blocking issues — ready to merge.

🔍 Technical details

Verification

• YAML parses (yaml.safe_load) ✅
• Every referenced path resolves in the current tree — tui/, src/gaia/daemon/, src/gaia/daemon/sidecars/, .github/workflows/build_tui.yml, and at least one hub/agents/*/python/packaging/ (email) — so no globs are dead on arrival.
• Structure matches the surrounding rules exactly; placement between the talk area rule and the hub-agent block is consistent with the file's ordering.

Non-blocking observations (no action needed)

• 🟢 sidecar (src/gaia/daemon/sidecars/**) is a subset of daemon (src/gaia/daemon/**), so files under sidecars/ receive both daemon and sidecar. Likewise hub/agents/*/python/packaging/** overlaps the matching agent::<id> label. This is the same intentional multi-label overlap already used by performance/llm/rag, so it's fine — just noting it's expected behavior, not a bug.

Strengths

• Forward-looking globs are all backed by real paths, and the test plan explicitly confirms the labels already exist as repo labels — avoids the common labeler failure mode of referencing a label that was never created.
• Clear comment block documents the milestone context and placement rationale.