Sync the API spec, docs and translations with the state rename and the new instance fields

The pre-alpha12 audit found the API spec, several doc pages and the French translations lagging the code after the engine status-to-state rename and the newer requester-facing fields (initiator, authored status).

D1 (major): the OpenAPI spec documents the pre-rename API. docs/openapi.yaml advertises a status query parameter and status schema properties, but the API serializes and filters state. It also omits the new instance initiator and authored status fields. Fix: rename the parameter and properties to state and add the two fields to the instance schemas.

G4 (minor): the client DTO omits the new instance fields. OrchestraClientInterface getInstance() and listInstances() expose only id, definition id, state, tenant and tokens, not the now first-class status, initiator, correlation key and definition version. No consumer breaks today. Fix: extend the DTO so a cross-site consumer can read them.

D2 (major): several doc pages still call the engine lifecycle "status". After the rename that noun names the authored vocabulary, so the engine lifecycle should read "state" in architecture.md, incidents.md, troubleshooting.md, retention.md, roadmap.md and versioning.md.

D3 (minor): the roadmap Built inventory omits the shipped requester surface (initiator, My requests page, status vocabulary, requester detail view). Fix: add them to the Built list.

D4 (major): about fifty work-item strings were stranded by the WorkItem code move. The assignment, work-item and timeout code moved from orchestra_inbox into the base module, but their French did not: those strings now have no msgid where the code lives, while dead entries sit in the inbox po file. Recent orchestra_ui (status vocabulary CRUD, My requests) and orchestra_interaction (message stacking) strings also have no msgid yet. Fix: move the stranded pairs to the base po, prune the dead inbox entries, and add the missing new-feature strings idiomatically.

D5 (minor): a banned arrow character in a UI string. OrchestraCmForm uses an arrow glyph in a details title, copied verbatim into its po file. Fix: replace it with a word or comma separator.

One merge request covering the spec, docs, DTO and translations.