Craft workspaces redesign: PR sequence status

Multi-product workspaces redesign for getsentry/craft. PR A (#847): merged. PR B (#848, schema/resolver/selector): all Bugbot findings fixed (42d17f0), adversarial review SOLID/MERGE, CI green — HELD pending Burak Yigit Kaya's manual review/merge. PR C (publish-state workspace threading): branched as feat/workspaces-threading off feat/workspaces-schema (not master) so PR B's resolver is available; will rebase if #848 changes. Research found only ONE functional gap — getPublishStatePath()/getPublishStateFilename() (src/utils/publishState.ts) lacked workspace in its key, risking same-repo/cwd/version workspaces overwriting each other's publish state (see [[NEW_PUBLISHSTATE_ENTRY]]). Everything else (version resolution, changelog, release branch naming, target providers) already flows through the workspace-resolved getConfiguration(), needing no code changes. Implemented + tested (5 new tests, 1093 passed, tsc/lint/prettier clean). PR C review/opening HELD until #848 settles to avoid basing on a moving foundation. Sequence: A✅ → B (awaiting merge) → C (implemented, held) → D (action-layer) → E (docs).