Add TypeScript language adapter

[pdd27673]

Summary

• introduce a source-language adapter boundary shared by extraction and change analysis
• add TypeScript and TSX support for exported surfaces, imports, tests, and package entry points
• detect TypeScript repositories during initialization and document the supported behavior and limits
• update the generated system map and add focused coverage for configuration, extraction, and change analysis

Verification

• uv run pytest -q (383 passed)
• uv run pre-commit run --all-files
• uv run systemap refresh
• uv run systemap check
• uv run systemap judgement
• git diff --check

[0xfauzi]

This PR is reviewed as part of #12. #12 contains this PR's commits, so the review is in one place: see the comment there.

I suggest closing this PR and continuing in #12. The layers of the stack change each other's behaviour. For example, #11 makes tsconfig.json required to detect a TypeScript repository, which #10 did not. So merging this layer on its own would ship a state that the next layer replaces.

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