feat(loop-context): add similarity-based stagnation detection

[THRISHAL12345]

Summary

Replaces exact string matching for error signatures with a highly robust Character Trigram Jaccard Similarity algorithm in loop-context, ensuring the circuit breaker trips on semantically-similar failures even if the phrasing or wording morphs slightly across iterations.

Changes

• New pattern or starter (followed templates/pattern-template.md + updated registry.yaml)
• Doc / example improvement
• Tool change (loop-context)
• Story (includes real failure or surprise + lesson)

Checklist (from CONTRIBUTING)

• All required sections present for patterns
• Links work from README, patterns/README, starters/README, docs/index
• No secrets, tokens, internal company URLs
• STATE.md* examples use .example suffix
• Safety-related content references docs/safety.md
• Ran node tools/loop-audit/dist/cli.js . (or on the starter) and addressed findings

Testing / Dogfood

• loop-audit passes on affected starters or this repo (Scored 100/100 L3)
• Manual review of generated state / skill output (Fully tested with npm run test inside tools/loop-context - all 49 edge-case and algorithm tests pass cleanly).

Screenshots / Examples (if UI or command output)

Running loop-context on slightly morphed failures:

$ loop-context --check --stagnation 3 --similarity-threshold 0.85 < run.json
ESCALATE [stagnation] — Same error repeated 3× in a row (threshold 3): "Error: connection timeout on port #". Escalating instead of retrying.

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[cobusgreyling]

Thanks @THRISHAL12345 — merged during scheduled maintenance. Similarity-based stagnation is a nice upgrade over exact-match signatures.