Per review: no dedicated coverage tool.
- index_status now carries the coverage report (parse_partial + skipped
lists from the separate index_coverage table, plus the best-effort
coverage_note); get_index_coverage is removed. Tool description
updated so agents learn the coverage semantics from index_status;
index_repository and the response note now point there
- the read hook resolves coverage through index_status (same envelope
fields, unchanged note wording); verified end-to-end against a real
index (flagged file -> note with exact ranges, clean file -> silence)
- get_code_snippet responses from a parse_partial file now carry a
correlated coverage_note ("line range(s) X could not be parsed ...
the source above is ground truth") — the result names its file, so
the warning is precisely anchored. Entirely-skipped files cannot
appear here (no nodes), so no uncorrelated noise is possible; clean
files carry no note (asserted both ways in the e2e test)
Refs #963
Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>