perf: cache file attribution for instant blame navigation

docs/architecture.md

@@ -51,7 +51,7 @@ Frontends borrow `top_bar_config()` and `bottom_bar_config()` for validated orde
 Frontends borrow `popup_config()` for independently configured command/search anchors. The TUI resolves each anchor against the chrome-free workspace using the existing bounded popup size; startup configuration does not alter buffer text, modal input, or notification positioning.
 Frontends borrow `lsp_label()` / `lsp_names()` for the focused buffer's cached ready-server metadata. Initialization-only worker events trigger status redraws independently of diagnostics; session synchronization clears or replaces names when focus changes or a server retires. `notification_visible()` gates persistent operation/diagnostic popups independently of stored message text, so Escape dismissal neither alters text nor collapses carets. Display-only home abbreviation does not change document identity.
 
-Current-line blame is enabled by default. Session schedules one request per focused tab/pane/buffer/text-revision/path/row identity and rejects superseded results, including results returning after navigation away and back. The editor stores a sanitized borrowed label; rendering uses only spare cells after the current logical line's final visible continuation and hides it when the primary caret is offscreen. Disabling drops the worker; comparisons and immutable buffers never schedule live blame.
+Current-line blame is enabled by default. Session loads whole-file incremental attribution into one active-buffer cache keyed by buffer/text/save revision, disk stamp, and path; cursor, tab, and pane movements within that source reuse it without copying file text or issuing repository commands. Cold results select the current row when they arrive. Edits, saves, source changes, disk refreshes, focus regain, and disabling invalidate attribution; stale results cannot replace a newer source. Metadata is shared per commit with `Arc`, and same-commit navigation reuses the sanitized label. Rendering uses only spare cells after the current logical line's final visible continuation and hides it when the primary caret is offscreen. Disabling drops the worker; comparisons and immutable buffers never schedule live blame.
 
 Frontends inspect `file_picker()` for query, presentation, view, explorer-local INSERT/filter subfocus, selection, and errors, and iterate borrowed `FileRow` metadata (actual path, display label, directory flag, visible depth, expansion). Dock side is a logical preference. They allocate rectangles, add folder suffixes/colors, and render; hierarchy, filtering, parent/child navigation, focus transitions, and selected-file opening remain backend-owned.
 Frontends inspect `diagnostics()` and `diagnostic_at_cursor()` for validated active-buffer annotations. Diagnostics are owned by core LSP or a plugin and buffer revision; text changes clear them. Native server retirement removes only that server's contribution, preserving sibling diagnostics. The TUI underlines annotated text, colors affected gutter numbers by severity, and displays the primary caret's diagnostic message without replacing search/selection backgrounds.

docs/editing.md

@@ -210,7 +210,7 @@ Text wraps at word boundaries where possible, with grapheme-safe breaks for long
 
 Inline blame is enabled by default in ordinary live file buffers. The primary caret's line shows its author, commit summary, and short commit ID after the document text; changed or newly inserted tracked-file lines show **Uncommitted**, including unsaved edits. Git-backed jj repositories use the working-copy revision's single parent, not a potentially stale Git HEAD. Merge working copies with multiple parents omit attribution.
 
-Loading happens in the background without network access or changing repository refs/checkouts. Missing, untracked, unborn, and non-repository files have no indicator; immutable historical buffers and comparison views do not receive live-file attribution. Moving, editing, switching views, or disabling clears stale results. The indicator is hidden when the caret is offscreen or the full label cannot fit; wrapped lines use their final visible continuation without covering text, selections, or the caret. Popups retain their normal layering.
+Loading happens in the background without network access or changing repository refs/checkouts. Attribution is loaded once for the active buffer's in-memory contents; navigation then selects cached lines immediately, and movement during a cold load does not restart it. Editing, saving, reloading, changing source buffers, regaining terminal focus, or toggling blame invalidates the cached attribution. Missing, untracked, unborn, and non-repository files have no indicator; immutable historical buffers and comparison views do not receive live-file attribution. The indicator is hidden when the caret is offscreen or the full label cannot fit; wrapped lines use their final visible continuation without covering text, selections, or the caret. Popups retain their normal layering.
 
 Use `:git_blame.toggle`, the palette action, or remappable `config.core.git_blame.toggle`; there is no default keybinding. Set `config.git_blame = false` to disable it at startup. Disabling stops the worker and clears the label without changing text or undo history.