feat: configure chrome segments and anchor groups

docs/architecture.md

@@ -9,6 +9,7 @@ Contributor-facing module boundaries and implementation contracts. Project termi
 One editor crate; the workspace also includes its patched Crossterm dependency. Terminal-coordinate types remain outside the editing backend:
 
 - `editor`: owns shared buffer lifecycle/text/saved state/undo history and independent tab/pane layouts, focused views, modes, selections, searches, explorers, and comparisons; session-wide clipboard policy, independent registers and owned-system fragment metadata, semantic native repeat, action metadata, command-palette and file-picker focus/dispatch, key notation, key-sequence/count prefixes and binding resolution, modal paste policy, saving, command ownership, capabilities, and validated edit effects. Its low-level interface returns an `Invocation` when an external command is selected.
+- `chrome`: owns validated tabline/statusline anchor groups, segment title templates and padding/edge options, builtin defaults, and named-value validation. It has no terminal geometry or render callbacks.
 - `files`: owns the gitignore-aware directory/file catalog, authoritative OS paths, compact tree projection, query filtering, browse/search focus, expansion/selection restoration, navigation, and scan/error state shared by floating and docked presentations.
   Virtual file leaves retain their original catalog input index for caller-owned annotations; scanned entries and directories remain unannotated.
 - `diff`: owns searchable Before/After selection, category, focus and explorer visibility, request freshness, read-only comparison DTOs, aligned rows with cached grapheme-level change ranges, and shared vertical/independent horizontal offsets. Changed paths form a virtual `files::FilePicker` catalog, reusing the normal tree projection, filtering, and navigation without scanning disk. It has no subprocess or terminal dependencies.
@@ -38,6 +39,7 @@ Frontends inspect `line_operator_pending()` for the optional Normal `d`/`c` pref
 Editor-owned jump history is a bounded 100-location `VecDeque` of buffer IDs and grapheme cursors plus a current index, with no copied paths/text. Successful high-level navigation records departure/destination once; traversal uses unrecorded buffer activation and position placement, skips closed/clamped-duplicate locations, and truncates forward entries only on a distinct new jump. Session synchronization permanently invalidates pending LSP position requests after their source buffer/revision/caret/mode is left, so returning through history cannot revive an old definition reply.
 Frontends inspect `buffer_id()`, `buffer_count()`, `has_buffer(id)`, and the ascending-ID `buffers()` iterator of borrowed path/dirty/active metadata. Existing text, cursor, selection, search, and mode methods describe only the active buffer.
 Frontends inspect `tab_id()` for stable identity, `tab_index()` for display order, `tab_count()`, and `tab_buffer(index)` for borrowed title metadata. `pane_layout()` describes only the active tab; globally unique pane IDs keep inactive tabs' viewports alive. Documents remain unique across all tabs, while independent pane/buffer views are parked and restored without copying text.
+Frontends borrow `tabline_config()` and `statusline_config()` for validated ordered left/center/right segment groups and effective segment styles, and `label(name)` for session-wide custom values. The TUI owns terminal-cell widths, full-row center anchoring, clipping, and accent styling. Label effects carry only a name and plain text; they are global presentation updates, not buffer/revision-bound results or render callbacks.
 
 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.
@@ -56,7 +58,7 @@ Redraws stage Ratatui's buffer diff, cursor placement, and DEC synchronized-upda
 
 `vendor/crossterm` retains Crossterm 0.29.0's upstream source and MIT license, with a small Unix decoder patch exposing `Event::ColorSchemeChanged` for `CSI ? 997 ; 1/2 n`. The report signals a palette refresh, not a choice of hard-coded light/dark colors. Valid fragmented reports and malformed color reports leave following keys intact. Cargo patches both direct and Ratatui dependency paths to this one copy; remove the patch/workspace member once upstream supports these notifications.
 
-The TUI uses Ratatui constraint-based layout for a flexible buffer viewport, a one-row status bar, and a one-row prompt/message area. Multiple tabs reserve a top row for numbered filenames, dirty markers, and active-tab styling; overflow keeps the active title visible. Scrolling, clipping, highlights, and cursor placement use the allocated regions, not terminal-wide offsets. Below three workspace rows the status bar is hidden; at one workspace row the buffer remains visible unless an active command/search prompt takes priority. Zero-sized terminals render nothing. Layout and terminal-cell text mapping remain frontend-owned.
+The TUI uses Ratatui constraint-based layout for a flexible buffer viewport, a one-row statusline, and a one-row prompt/message area. Multiple tabs or visible custom top-line segments reserve a tabline row; overflow keeps the active tab title visible. Each chrome row renders configured ordered left/center/right groups, with center anchored to the full row rather than the remaining gap. Padding is inside segment styling, while leading/trailing edge glyphs are separate terminal-cell-width decorations. Scrolling, clipping, highlights, and cursor placement use the allocated regions, not terminal-wide offsets. Below three workspace rows the statusline is hidden; at one workspace row the buffer remains visible unless an active command/search prompt takes priority. Zero-sized terminals render nothing. Layout and terminal-cell text mapping remain frontend-owned.
 
 Mouse wheel input uses the last rendered document/panel rectangles for hit-testing. Document offsets and explorer scroll state remain frontend-owned; three-row wheel steps never become document cursor motions. Manual document views persist until logical caret-reveal, caret/selection, mode, revision, or buffer changes; offscreen primary and browsing-selection cursors are not placed. Hover wheel input reuses the existing editor-owned popup scrolling.