* refactor(sessions): add dormant JSON-backed SessionDB adapter (#3720, #3383)
First, lowest-risk slice of the unified-session-db migration: a SessionDB-shaped
adapter over the existing WebUI JSON store, behind a dormant experimental flag
(experimental.unified_session_db, default false). No runtime call site is rewired
— is_unified_session_db_enabled() has no live callers, so persistence behavior is
unchanged until a later migration PR opts in. Includes the adapter, the dormant
config flag + _apply_config_defaults wiring, an architecture doc, and adapter tests.
Also adds docs/architecture/ to the .gitignore docs allowlist (the docs/* rule
excludes subdirectories; the new architecture doc and its presence test would
otherwise be silently dropped on a clean checkout).
Co-authored-by: rodboev <[email protected]>
* docs(changelog): stamp v0.51.305 — Release JU (stage-p2b #3720)
---------
Co-authored-by: nesquena-hermes <[email protected]>
