Fix #282: lenient type coercion for workflow StructuredOutput

[ericleepi314]

Closes #282

Stacked on #314 (deep stack down to #304). Merge in order; GitHub retargets automatically.

Summary

Weak models (glm) return JSON types as strings — "42", "true", arrays as JSON-encoded strings — and the workflow engine's strict StructuredOutput validation burned all schema-repair retries on trivially coercible mismatches (PR #266's known follow-up).

coerce_to_schema(obj, schema) — a lenient, never-raising pre-pass run before strict validation in StructuredOutputCollector.offer:

• Keyed strictly on what the schema expects (never guesses from the value): "42"→42 for integer, "3.14"→3.14 for number, "true"/"false"→bool for boolean, JSON-encoded strings→json.loads for array/object (type-checked, then recursively coerced), integral floats→int for integer.
• Recursive through properties/items; type may be a string or list; anyOf/oneOf deliberately untouched (documented).
• ajv coerceTypes parity (from critic review against the reference semantics): "3.0"→3 for integer-only schemas; a string already satisfying a union with "string" is never rewritten; "NaN"/"Infinity" strings are rejected (parse as floats but aren't valid JSON numbers — the critic caught that they'd silently enter the output contract); bools never become ints.
• Anything uncoercible passes through unchanged so strict validation reports the real error and the repair-retry loop still works.

The injected tool now records collector.value (the coerced shape) in the outbox and tool result, so every consumer sees the same schema-conformant object.

Test plan

• 26 tests: per-rule units, an end-to-end glm-shaped fixture (every scalar stringly-typed, array JSON-encoded → accepted on attempt 1), NaN/Infinity rejection, "3.0"/"3.5" integer-only behavior, string-union no-rewrite, bool-never-int, uncoercible pass-through, genuinely-wrong-output still errors/exhausts
• Full workflow suite: 172 passed
• Full suite on the stack: 7865 passed, 0 failed, 5 skipped
• Critic review loop: APPROVE after 1 revision round (NaN/Infinity acceptance + ajv-conformance gaps came out of it, verified by execution)

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