chore(loop): let workflow_dispatch fall back to the write switch

[Alex1990]

A one-line bug with exactly the wrong blast radius: the entry point a human uses to test the write switch could never exercise it.

The bug

LOOP_EXECUTE_WRITES: ${{ github.event.inputs.execute_writes || vars.LOOP_EXECUTE_WRITES || 'false' }}

The input declared default: 'false', so GitHub filled github.event.inputs.execute_writes with the non-empty string 'false' on every manual run and the || short-circuited there. vars.LOOP_EXECUTE_WRITES was unreachable.

Verified on run 35002295453 with the repository variable already set to true: the payload showed "execute_writes": "false" and the engine logged writeLevel=report.

Schedule / issues / pull_request runs were unaffected — github.event.inputs is null there, so the fallback worked. That made it worse rather than better: the loop would have started writing on real events while the switch appeared broken in the one place you would look to confirm it.

The fix

Drop the default:, making the input tri-state and the expression mean what it reads:

dispatch	result
input empty	follows vars.LOOP_EXECUTE_WRITES
-f execute_writes=true	writes, for that run
-f execute_writes=false	reports, for that run

Both directions verified on Actions, dispatched against this branch (--ref):

$ gh workflow run loop.yml --ref fix/loop-execute-writes-fallback -f smoke=true
 [loop] ... · writeLevel=auto        ← falls back to the variable

$ gh workflow run loop.yml --ref fix/loop-execute-writes-fallback -f smoke=true -f execute_writes=false
 [loop] ... · writeLevel=report      ← explicit override still wins

smoke=true was used for both probes: it skips the agent and never reaches applyActions, so neither run wrote anything anywhere.

scripts/loop/README.md records the tri-state semantics and why the input must stay default-less — the failure mode is invisible from the workflow file alone, so the next person to add a "sensible default" needs to know it is not one.

Not in this PR

Nothing else about the switch changed. First real auto execution is still pending (see #46): it needs a claimable task, and the state layer currently has none — all 14 tasks are terminal or waiting-human.

[github-actions]

Coverage

Metric	%	Covered / Total
Lines	90.19%	1003/1112
Statements	89.06%	1083/1216
Functions	91.03%	193/212
Branches	76.43%	519/679

[github-actions]

Loop triage — needs-triage (human review + merge).

PR #47 edits the loop host's own machinery (.github/workflows/loop.yml and scripts/loop/README.md) on a same-repo branch fix/loop-execute-writes-fallback with no loop-task: marker. loopTaskOf() returns null, so the router sends owner repo PRs to triage: it is not a loop PR, and the loop must not be maker or checker for the change it runs on. It also touches .github/workflows/**, which the job token can never push — so there is no agent-actionable work here even in principle. What remains is a maintainer review/merge decision.

The bug and the fix both check out against live Actions logs:

• Bug on main — run 35002295453, workflow_dispatch with no input: payload "execute_writes": "false", engine log LOOP_EXECUTE_WRITES: false … writeLevel=report. The default: 'false' injected a non-empty string, so vars.LOOP_EXECUTE_WRITES was never reached.
• Fix, automatic direction — run 35002456149 on the fix branch, input left empty: LOOP_EXECUTE_WRITES: true … writeLevel=auto.
• Fix, explicit override — run 35002567015 with -f execute_writes=false: LOOP_EXECUTE_WRITES: false … writeLevel=report.

Both fix-side probes logged smoke mode: skipping the agent, so nothing was written. entry.mjs resolves the level fail-closed (=== 'true' ? 'auto' : 'report'), and the parallel smoke input keeps its default because it has no vars fallback — that one is harmless. CI on head 0cb7063 is green (Lint ✅, Test ✅); the pending loop check is this triage run. mergeable: MERGEABLE, mergeStateStatus: BLOCKED (review required by the Main branch ruleset).

One point for the reviewer: the commit/title type is fix(loop):, but AGENTS.md reserves fix for changes a package consumer can observe and requires chore(loop): for loop maintenance — fix is rendered into the user-facing CHANGELOG.md. Retitle/squash as chore(loop): when landing.

Proposed action: label needs-triage; a human reviews and merges. The loop must not merge it.