fix(errors): a Router bucket outranks the status table on every status

[mattmillerai]

Problem

A Router error response names its own bucket — the X-Comfy-Error-Type header, repeated as the body's top-level error_type — but the decoder only let that bucket through on 409 and on statuses the status table did not name. Everywhere else the table won and destroyed the bucket before anything downstream could read it:

• a 403 not_enabled surfaced as Forbidden, so except NotEnabled — the one handler every pre-launch caller writes — never fired (reproduced live: a not-yet-enabled account got Forbidden from models.run)
• a 422 invalid_input surfaced as InvalidWorkflow (a jobs-surface class), which is what every reachability probe tripped over
• a 404 model_not_found surfaced as plain NotFound

Fix — two halves

comfy_low.errors: precedence is now envelope error.code → wire bucket when one is present → status table. Only responses that carry a bucket retype, and only Router sends one; the v2 envelope and bucket-less responses (including a bare 429 → QueueFull) decode exactly as before.

comfy_sdk.exceptions.to_sdk_error: a preserved router-only bucket now raises its typed RouterError subclass (NotEnabled, InvalidInput, ModelNotFound, ConcurrencyLimitExceeded, …) instead of a bare ComfyError. The three buckets both surfaces spell identically (unauthorized, forbidden, insufficient_credits) deliberately keep their v2 classes — the code string alone cannot say which surface answered, and those classes catch on both.

Retry pacing is keyed on status + Retry-After and is unchanged; the collect rule on 409 concurrency_limit_exceeded is unchanged.

Tests

• Table-driven: the bucket survives on 403/404/409/422/429/500, with Retry-After intact
• Router-only buckets raise their typed classes across 7 statuses; overlapping buckets keep their v2 classes
• Bucket-less and v2-envelope decoding pinned unchanged
• One prior test asserting the old precedence (429 + bucket → queue_full) is rewritten to the new invariant — that test encoded exactly the behavior this PR removes
• Full suite: 718 passed locally (ruff, mypy, format, hygiene all green)

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[robinjhuang]

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