Complete tasks 3-7: harden verdict parsing, outputs retention, base branch, linux schedule parity, claim loop task

tasks/complete/harden-parse-verdict/BUG_REPORT.md

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+# Bug Report: harden-parse-verdict
+
+Bug_find phase observations. Each non-blocking unless marked BLOCKER.
+
+## O1 — `bool(raw_pass.strip())` fallback for "0" / "1" strings
+
+For `{"pass": "0", "score": 0.5}`, the new path strips → "0" → not "true"/
+"false" → `bool("0")` = True (non-empty string is truthy).
+
+Pre-fix: `bool("0")` was also True (same).
+
+This is **consistent with v1** — no behavior change. A verifier emitting
+`pass: "0"` intending "false" gets `True` in v1 AND in the hardened
+implementation. The SPEC says non-`true`/`false` strings fall through to
+`bool(...)`, which is truthy for non-empty. Not a regression.
+
+**Not a bug** — documented behavior per SPEC R1 + D-V1. If users want
+strict numeric-string handling, that's a separate future task (out of
+scope for v1.1 harden-parse-verdict).
+
+## O2 — `float("nan")` serializes back as `NaN` to `.state.loop`
+
+When the verifier emits `NaN` as the score, `parse_verdict` returns
+`score=0.5` (without writing to disk by itself). But this score is part
+of `verdict` which gets written via `_write_state_loop(loop_path, state)`
+into `.state.loop` as JSON. Since the clamp converts NaN to 0.5 BEFORE
+the verdict is stored, `.state.loop` gets `0.5`, not `NaN`. No NaN leaks
+into the loop state.
+
+**Not a bug** — confirmed via tracing: `parse_verdict` returns the clamped
+dict; `cmd_tick` then stores `state["last_verdict"] = verdict` (a clean
+dict with `score: 0.5`); the JSON round-trip is clean.
+
+## O3 — `_gate_score_plateau`'s threshold unaffected
+
+`_gate_score_plateau` (status.py) reads `score_history` and decides a halt
+when last N scores are within some delta. With clamped scores, the plateau
+detection range is now strictly `[0, 1]` instead of `[any, any]`. Brief
+review:
+
+- Pre-fix: a verifier could emit `score: 1.5` across N ticks; plateau
+  detection sees a flat line at 1.5; halt fires. Expected behavior.
+- Post-fix: the same verifier's 1.5 clamps to 1.0 across N ticks; plateau
+  sees flat line at 1.0; halt fires. Same outcome.
+
+- Pre-fix: a verifier emits alternating `0.9` and `1.1`; plateau sees a
+  bimodal history [0.9, 1.1, 0.9, 1.1] — NOT plateau (variation > epsilon).
+- Post-fix: alternating `0.9` and `1.0` (1.1 clamps to 1.0); plateau sees
+  [0.9, 1.0, 0.9, 1.0] — still variation above a small epsilon — still NOT
+  plateau. Same outcome in this scenario.
+
+Edge case: a verifier emits all `1.0` and `0.99` (vs 1.0 and 1.0 clamped).
+The clamp DOES change plateau detection in this case — `1.0 1.0 1.0`
+looks more plateau-like than `1.0 0.99 0.99`. Could cause halt earlier than
+prior. Documented as a desirable side effect (clamp reduces the verifier's
+untrustworthiness from inflating scores; plateau detection is more
+honest).
+
+**Not a bug** — improved behavior. Documented in CHANGELOG.
+
+## O4 — Verifier prompt hasn't been updated
+
+`prompts/loop-verifier.md` still asks the model to emit JSON with
+`"pass": true/false` and `"score": 0.0-1.0`. The runner now defensive-coerces,
+but the prompt's contract is unchanged. Was the prompt already
+JSON-typed-booleans-only? Let me check.
+
+**`prompts/loop-verifier.md` review**: still says "Output: strict JSON, no
+prose" with example shape. The prompt explicitly tells the model to emit
+JSON booleans — no mention of string-typed `pass`. So the v1 contract was
+strict; the O6 finding was a defense-in-depth concern, not a present-fault.
+The harden task adds belt-and-suspenders without changing the contract.
+
+**Not a bug** — the prompt remains authoritative. No edit needed.
+
+## Verdict
+
+**No blockers.** Proceed to adversarial_bug_find.