Migrate test surface to URI-string keys; add out-of-workspace file (persisted
in global storage) + untitled-buffer (in-memory, not persisted) cases; assert
F6 toggle works with no folder open. No LLM.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
F6 no longer requires a workspace file. It gets its own diffable predicate
(any file: or untitled:) decoupled from F2 isTracked, keys baselines by a
sha256 of the document URI, and stores them in VS Code GLOBAL storage
(context.globalStorageUri) — always present, never the repo (INV-19). Untitled
buffers have no durable identity → in-memory baseline only (lost on reload).
DiffViewController is now constructed before the workspace-root check and its
commands are always live (never stubbed) — the machine-landing advance wiring
stays in the with-root branch since the seam only fires on workspace files.
BaselineStore generalized to key-by-hash (Baseline.docPath → uri).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>