feat: enhance string literal extraction and documentation matching

[oarisur]

• Added a new function extractStringLiterals in diff-parser.ts to capture meaningful string literals from changed lines, filtering out common non-architectural strings.
• Updated parsePRFiles to include extracted string literals alongside changed symbols.
• Introduced a regex in doc-extractor.ts to capture quoted string values from documentation, aiding in matching diffs that change string literals.
• Modified findCandidateSections to incorporate changed literals from the diff for improved section scoring.
• Increased the threshold for candidate section matching in drift-detector.ts from 3 to 6 to refine detection accuracy.
• Updated ChangedFile interface in types.ts to include changedLiterals for better data structure representation.

[github-actions]

🧠 Knowledge Diff — Rationale Drift Detected

I found 2 documentation drift issue(s) in this PR. The code changed, but the docs didn't keep up.

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🔴 __tests__/fixtures/diffs.ts → README.md — Configuration

Definite contradiction: The documentation states the default OpenAI model is gpt-4o, but the code has changed it to gpt-4o-mini.

Doc still says:
"gpt-4o / claude-3-5-sonnet-20241022 / gemini-2.5-flash"

Suggested update:

- `gpt-4o` / `claude-3-5-sonnet-20241022` / `gemini-2.5-flash`
+ `gpt-4o-mini` / `claude-3-5-sonnet-20241022` / `gemini-2.5-flash`

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🔴 dist/index.js → README.md — What It Does

Definite contradiction: The documentation states that Knowledge Diff reads 'what functions changed, what lines were added/removed' from the code diff. However, the code now explicitly extracts 'meaningful string literal values' from changed lines, which is a new type of information being processed.

Doc still says:
"what functions changed, what lines were added/removed"

Suggested update:

- what functions changed, what lines were added/removed
+ what functions, string literals, and lines were added/removed

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No drift detected in 10 other changed file(s).

📝 Auto-patch available: I've opened PR #27 with suggested doc updates — review and merge when ready.

_{🧠 knowledge-diff • 27 candidate pair(s) checked}