fix(run): stop per-pass advisory churn on large catalogs - #334

Problem

Even with a correct watch, each reconcile pass on large catalogs repeated identical advisory work: for every agent workspace that is not inside a Git repository, materialization spawned git rev-parse (plus captured stderr) only to fail, and print_report re-printed the identical warning every pass. Measured live on an oversized production catalog: ~28 failed spawns per pass at a spun-up cadence, 7,028 duplicate warning lines in hours.

Goal

A persistent advisory failure costs one spawn-free answer and one diagnostic line — not per-pass churn.

Decisions

• Marker probe before spawn: git_exclude now checks for a .git entry up the ancestor chain (the exact probe is_git_tracked already uses) and answers "not a Git worktree" without a process. .git may be a directory or file (linked worktrees); exists covers both. If a workspace later becomes a repo, the probe succeeds again and the real git path resumes — no cache to invalidate.
• Recurring-warning dedup in the supervisor loops: warnings persisting across passes are emitted once; if the condition clears and returns, it is surfaced again. Applied to both the catalog loop (up_loop_until) and the spec loop (up_loop_specs). This mirrors the existing reported_flapping pattern.

Verification

• New unit test: git_exclude on markerless workspace fails with "no .git marker" without touching git; a .git directory above re-enables the git path.
• New e2e test drives up_loop_until over a catalog whose agent declares render { git-exclude } with a non-Git workspace: several passes run, exactly one warning is delivered.
• Live reproduction (synthetic catalog, four non-Git workspaces, 1 s interval): each of the four warnings printed once across eight passes; idle CPU 3 ticks / 4 s.

Complexity

One helper function plus a two-method dedup struct. No new dependencies.

Concerns

• Dedup applies to all supervisor warnings, so genuinely intermittent-but-identical warnings appear once per continuous occurrence rather than per pass. That is the intended semantic ("diagnose once while unchanged").

References

Part of the #314 stack. Base: #318 (sidecar watches).