docs(file-ipc): audit legacy file IPC surface and FileStorage consumption

Add two audits under v2-refactor-temp/docs/file-manager/:

- legacy-file-ipc-audit.md: current-state inventory of all legacy File_*/Fs_*/Open_Path channels (FileManager.ts Group A + ipc.ts Group B) with registration points and every renderer consumer (file:line).

- filestorage-consumption-audit.md: per-consumer verdict (reroute / abolish / defer) for the 25 v1 FileStorage-backed channels against the target IpcApi (RFC §7.2), with rewrite sketches. Records a BLOCKING prerequisite (§7): unify the branded absolute-path type (FilePath / AbsolutePathSchema) before migrating consumers.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: eurfelux <eurfelux@gmail.com>

Author: EurFelux