fix(tool): preserve Python header documentation

[Copilot]

TestPython generated bindings without comments from declarations in Python headers. Clang requires -fparse-all-comments to expose these ordinary C comments.

• Generation: Add KeepDoc support to tool configuration; when enabled, parse headers with -fparse-all-comments.
• Python fixture: Enable KeepDoc and update generated goldens with the extracted comments.

{
  "KeepDoc": true
}

• Fixes fix(tool): TestPython bugfix - keep doc #927

[xushiwei]

@copilot The tool package does not offer an option to disable doc extraction, so there is no need to add the KeepDoc configuration item.

[fennoai]

Review: fix(tool): preserve Python header documentation

The change is small, well-scoped, and backward compatible. Adding an opt-in KeepDoc config that threads -fparse-all-comments into clang is the right mechanism for surfacing ordinary C header comments, and refactoring ParseSources into a public wrapper + private parseSources(..., keepDoc) preserves the existing exported signature — good call. The fixture llcppg.cfg plus regenerated goldens give regression coverage.

One substantive question and a couple of doc nits below. No blocking issues.

Design note worth confirming (not necessarily a bug): cfg.KeepDoc is threaded only into the clang parse flag; NewPackage never sets cl.Config.DontKeepDoc, so cl's internal keepDoc is always true in the tool path (comment emission is always on). In contrast, the test harness ties the two together via DontKeepDoc: !conf.KeepDoc (cl/compile_test.go:111). So in the tool path, KeepDoc=false still emits Doxygen-style doc comments and only suppresses ordinary comment parsing — which may well be intended, but the asymmetry with the cltest path is easy to trip over. See the inline note on tool/gen.go.

[Copilot]

@copilot The tool package does not offer an option to disable doc extraction, so there is no need to add the KeepDoc configuration item.

Removed KeepDoc and made -fparse-all-comments unconditional in tool parsing. The Python fixture and llgo test ./tool/... pass. Commit: d673211.