The mergemaster gates run rustfmt and rejected 864's merge because
several files I added/touched in master today had not been fmt'd.
Six files affected, mostly trivial line-wrapping nits. Fixes the
formatting gate for the next 864 merge attempt.
Before: tool_run_check (and run_build/run_lint via run_script_tool)
returned the entire cargo log verbatim in `output`. For runs with many
errors the response routinely exceeded the MCP token cap, was dumped
to a tool-results file, and the agent had to scrape it with python3
just to see the error list — burning many turns on file archaeology
for what should be a one-look operation. Real example: 864's coder
hit `result (143,708 characters) exceeds maximum allowed tokens` and
spent ~8 turns extracting 3 errors.
Now:
- New `service::shell::parse_diagnostics` parses `error[CODE]:` /
`warning[CODE]:` headers + their `--> file:line` markers into
structured `Diagnostic { kind, code, message, file, line }`.
- `tool_run_check` (and the run_build/run_lint shared body) returns
`{ passed, exit_code, errors: [...], warnings: [...], summary }`.
Raw `output` is dropped from the default response.
- New `verbose: bool` argument (default false) restores the raw
output for callers who actually need it.
- Updated the existing tool_run_check test to assert the new
contract (150 errors → 150 structured entries, response < 50KB).
Skipped run_tests in this pass — its parser would need to recognise
test-runner output (different format from cargo); will land separately.
Closes 886.
dave