feat: smart PCH rebuild, #include/import completion, rapid-edit robustness (#394)
## Summary
### Preamble completeness check
- `is_preamble_complete()` in `scan.cpp`: checks whether
`#include`/`import`/`export module` directives in the preamble region
are syntactically complete (have closing `>`/`"`/`;`)
- `ensure_pch` defers PCH rebuild when preamble is incomplete (user
still typing), reuses old PCH instead of failing
### #include / import completion
- Master intercepts completion requests in `#include "..."` / `#include
<...>` / `import ...` contexts before forwarding to worker
- `complete_include()`: searches include paths (from compile args via
`SearchConfig`) using `DirListingCache`, supports
quoted/angled/multi-level paths
- `complete_import()`: filters `path_to_module` map by prefix
- Word boundary checks prevent false matches (e.g. `important` not
treated as `import`)
### Detached compile task (rapid-edit fix)
- Compile operations (`ensure_deps` + `send_stateful` +
`publish_diagnostics`) run as detached tasks via `loop.schedule()`,
independent of the LSP request coroutine chain
- LSP `$/cancelRequest` can no longer kill in-flight compilations —
previously, cancellation would destroy the `ensure_compiled` coroutine
frame, leaving `doc.compiling` permanently set and hanging all
subsequent requests
- `CompileGuard` RAII ensures `doc.compiling` is always cleaned up even
if the detached task fails
- Stale feature requests (where `ast_dirty` became true after compile
finished) are dropped before forwarding to worker
### Other fixes
- `signal(SIGPIPE, SIG_IGN)` on POSIX: prevents server crash when LSP
client disconnects mid-write
- `CompilationUnitRef::file_path()` / `deps()`: null-check
`FileEntryRef` to prevent segfault on invalid FileID
- `stateless_worker.cpp`: log BuildPCH diagnostic errors for
debuggability
- Default worker counts changed to 2 stateful + 3 stateless
- `logging_dir` default changed to `.clice/logs` in config
### Tests
- 19 unit tests for `is_preamble_complete` (incomplete `#include`,
`import`, `export module`, mixed cases)
- Integration tests: `test_include_completion.py` (5 tests),
`test_import_completion.py` (4 tests), `test_rapid_edit.py` (2 tests),
`test_pch.py` (4 new tests)
- Smoke test: `rapid_edit.jsonl` — recorded VSCode session with 40 rapid
edits + 61 cancel requests
## Test plan
- [x] Unit tests: 463 passed
- [x] Integration tests: 104 passed
- [x] Smoke test (rapid_edit.jsonl): PASS
- [x] Manual VSCode testing with `#include <iostream>` project
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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