docs(benchmarks): record the CG-36 cluster-starvation measurement

The issue blamed the density tiebreak; both real cases lost on maxImportance,
so ranking was left alone. Full before/after table, the one cost (okhttp's
rank-6 file, squeezed out by reservations that were already structurally
over-subscribed), and what ships to keep it measurable.

CHANGELOG.md

@@ -34,6 +34,7 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 - When a `codegraph_explore` answer runs right up against its size limit, it now drops the trailing notes rather than a whole file's source. Previously the last file was cut even though trimming the notes alone would have fit, so a file that had already been read, ranked and rendered was thrown away at the last moment. Across a range of real projects this returns one more file and up to 20% more source per call.
 - Every file `codegraph_explore` decides to include now actually arrives. A file shown in full could still spend room set aside for files below it — the fix above covered files shown as excerpts but not files shown whole — and the answer's own size bookkeeping under-counted each file's heading, so the answer ran past its limit and a fully prepared file was discarded at the end. A file that no longer fits whole is now shown as excerpts instead of vanishing, and one that overshoots by a little is trimmed to fit rather than dropped.
 - The list of files an answer could not cover — the "explore these names for their source" pointers — is no longer thrown away when the answer is full. It is now budgeted for and trimmed to fit, so a full answer still tells you what it left out and which names to ask for next, instead of ending with no pointers at all.
+- When a `codegraph_explore` answer shows a file as excerpts, a large excerpt that no longer fit was dropped entirely instead of being shortened. If the file's first excerpt happened to be a trivial one — an import block, a one-line helper next to the code you asked about — the excerpt carrying the actual answer was the one thrown away, and the file came back with a quarter of the room it had been given. On real projects that meant the top-ranked file delivered a fraction of its share while a far less relevant file took the rest. Excerpts are now shortened to fit, whole method by whole method, and only dropped when what is left is too small to hold anything readable.
 - The blast-radius section of `codegraph_explore` flagged "no covering tests found" whenever no test called a symbol directly — falsely branding helpers that tests exercise through their callers as untested (about 40% of flagged symbols in a measured sample). The check now follows caller chains up to 3 hops and reports indirect coverage as "tested via callers"; when nothing is found it states exactly what was checked instead of an unconditional warning. Thanks @inth3shadows for measuring the false-positive rate. (#1475)
 
 ## [1.5.0] - 2026-07-21