Trains 26c + 27: parser-decided whereis, std-member honesty, call sites first, proven implementors, lean grep/impact/whereis, #362, #339

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This PR carries train 26c and train 27 together (26c's PR #384 is green but never received an automated review; its commits are the first part of this branch, and merging this PR merges #384).

Train 26c (see #384 for the per-lane table)

whereis definitions from the parser (and refs read from tree objects), owner hop, map inventory, lean expand, CLI speed (~¼ less per warm call; --whereis on many-branch checkouts ~70% less), #358 import capture (JS/TS + Go slices), honesty-small-b, #362 (budgeted-bundle candidate page, @pt-act), #339 (Rails db/schema.rb columns, @mpapis), plus the #383 CodeRabbit Minors.

Train 27

lane	what it changes
cpp-builtin-member-gate	A C++ call to a standard-library member name (size, empty, find, push_back, …) on an unproven receiver no longer splits over in-tree definitions of that name; it is declined and listed (<stdm>). A receiver whose written type names an in-tree class (incl. through unique_ptr/shared_ptr/optional, wrapper templates and typedef/using aliases) keeps its hedged edge.
callers-sites-first-call	--callers / --safe-delete list call sites as file:line in the first answer (sites_at=), matched by leaf name on any receiver; a cut list says so and next= recovers the rest.
lego-transitive	--lego lists transitive implementors through PROVEN extends/implements/include edges only; a name-only base is hedged (base_by="name"), a base the evidence puts elsewhere is left out and counted, and the walk's stop below an unproven direct row is disclosed (transitive_unwalked=). Ruby include/extend and JS factory classes are covered.
lean-trio	--grep serves the string tier for text-shaped literals when code hits are few; --impact adds a per-file rollup beside a cut window; a clean-tree --quality-delta / --edit-check prints its verdict, folding only rows that cannot answer the question (only at HEAD, only when the fold saves >= 25%, every row recoverable).
seams-doc-links	Links between two document sections are no longer counted as code seams; layer="test" is spelled only for a file under a test directory whose dependents are all test paths.
whereis-lean	A --whereis row's line text over 300 B prints as a 200 B preview (cut on a UTF-8 boundary) only when that makes the page shorter; --whereis-full-text (MCP full_text) replays the same page whole-line. Peak memory on the parse-guard path drops ~0.5 GB.

Also: CONTRIBUTING gains "Feature families: one shared handler each" (the common-code plan in public form).

Pins: kParserVer 164, kCacheVersion 31, kQSnapCacheScheme 20 (test/qschemetrip.hash re-derived once). Generated docs regenerated once from the merged binary.

Checked: every lane was reviewed (each needed at least one fix round) and signed; a pre-review pass over the conflict-resolved and new hunks; byte identity 32/32 against the 26c head outside the lanes' scope. One known red at this head — compactlegendcheck (P1-B): under an explicit --token-budget, the compact answer can exceed both the budget and the full answer at some budgets (a 26c regression, bisected to the lego-charge merge); its fix lands on this branch before merge.

🤖 Generated with Claude Code

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