Four fixes to the tool-search deferral layer, split from PR #92693 (the
availability-cache staleness fix ships separately):
1. The parallel batch planner now peels the tool_call bridge wrapper and
decides admission on the underlying tool — supports_parallel_tool_calls
works again when deferral is active. Unparseable wrappers stay
sequential barriers; bridged calls get exactly the admission the same
call gets direct. tool_search/tool_describe lookups batch concurrently.
2. _short_desc no longer truncates listing lines at 'e.g.', hostnames, or
version strings — a sentence terminator must be followed by whitespace.
3. BM25 indexes the source label (e.g. 'linear' for mcp-linear), so
service-name queries reach tools whose own name omits the service; the
dead 'mcp' prefix token is stripped.
4. Substring-fallback docstring corrected (token misses, not zero-IDF).
Salvaged from #92693 by @alt-glitch with authorship preserved.
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