fix(devx): mark dead watch-hint literals in reachable families and refuse @-scoped specifiers as paths (#13447)

Three of the five hints --residue showed for check:query-options-erasure
named files that have never existed, printed verbatim: the annotator only
spoke when a WHOLE family was unreachable, so one live baseline walked its
dead siblings past every reader unlabelled. Measured across all families
before choosing the route: 65 of 151 declaring families carried 598 such
literals, 353 of them @-scoped package specifiers.

- deadHintSweep: the reachability sweep at per-hint grain; the unreachable
  listing and the new residue annotations read one sweep, two grains.
- residueNames / deadNamesNote: dead literals are marked where shown and
  counted with reasons where not.
- isNonPathNamespace: an @-headed first segment (npm scope, version-suffixed
  specifier, bundler alias) is a namespace, not a path — 353 dead hints
  refused at extraction, zero tracked paths start with @, no live hint moves.


Claude-Session: https://claude.ai/code/session_01Pk26oZ12t5N1hwGW1m1MgC

Co-authored-by: Claude <noreply@anthropic.com>

Author: os-project-manager