feat(ui): dead code and islands — what nothing reaches, and everything that could still reach it (CG-59)

A Dead code screen and a mark on the Map, both drawn from one derivation in
src/graph/dead-code.ts so a second surface can never disagree with the first.

The SQL half is four lines — no incoming edge but `contains`. It returns ~2 500
candidates on this repository and the shipped list is 20; everything in between
is the feature. A candidate is dropped the moment there is any reason to believe
something outside the graph reaches it: exported symbols and header
declarations, test and generated files, abstract and interface members, anything
carrying a `decorates` edge, overrides of an ancestor's member, names the
language calls by itself, vendored directories, files nothing in the index
reaches (those are islands, and the Map says so instead), names the resolver
failed to resolve somewhere, and names shared with a symbol that IS referenced —
the mis-resolution that leaves a used method with a self-edge and its twin with
nothing. The last rule is the only one that is not a graph query: before a claim
is made, the declaring file and every file that reaches it are read and the
identifier counted, which is what catches the references the extractor never
recorded (`this.handleMessage.bind(this)`, a call inside an object literal, a
shorthand property).

Every subtraction is counted and printed under the list with the scale it came
from, and the caveat line above it never collapses: the claim is "no static
reference in the index", not "unused".

On the Map a module nothing depends on keeps its stroke and says so in its count
line, and tool-generated files and modules recede to ink-4 there, in the map's
file list, in search results and on the file screen.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/design/codegraph-ui-design-spec.md

@@ -337,6 +337,46 @@ Nothing in the engine emits an `overrides` edge, so this is a NAME match inside
 says so. It is deliberately blind to signatures — an overload set would need type resolution the graph does not have.
 Layout is arithmetic (row height × index): no `ResizeObserver`, no measurement, same payload → same picture.
 
+### 3.11 Dead code and islands (CG-59)
+A screen (`#/dead`, `?exported=1`) and a mark on the Map.
+
+**The list.** Symbols no import, call or reference in the index reaches, ranked largest first and grouped by file with the
+Symbol view's `.filegroup` / `.row` shapes (design spec §3.2) — file path 11px mono `--ink-3` with the group's
+"N symbols · M lines" opposite it, then rows of kind glyph + 12.5px mono name + 11px mono `file:line` + an 11px `--ink-3` meta
+line ("method · 51 lines"). A dead container folds its unreachable members into a wrapped strip of 11px mono links under it
+rather than listing them as siblings — one finding, not eleven. Column max-width **760px**, 40px gutters, exactly like the
+entry-points panel.
+
+**The caveat is part of the screen, not a note on it.** A persistent 11.5px `--ink-3` line sits above the rows, between two
+hairline rules, and never collapses or dismisses: *"No static reference in the index — dynamic use is possible."* Under the list,
+every reason a candidate was left off is printed with its count ("1 677 in test files", "378 exported, or declared in a header",
+"40 overriding a member declared further up"), preceded by the scale — *"2 494 symbols in this index carry no incoming reference
+at all; 2 474 of them were left off this list."* Twenty rows drawn from twenty candidates and twenty drawn from two and a half
+thousand are different screens and only that sentence tells them apart.
+
+**One switch**, an 11px mono chip on the right of the caveat bar: `Internal only` (default) ↔ `Including exported`, carried in
+the URL. Turning it on adds symbols something outside the repository could import, and the screen grows an `--accent-soft` band
+with an `--accent-line` border saying so; each such row also carries an `exported` chip. Exported rows are never on the default
+list, because the index cannot check a caller it does not contain.
+
+**Islands, on the Map.** A module no link in the payload arrives at keeps its normal 1px `--ink` stroke — it is not a lesser
+module, it is an unreached one — and its 11px count line reads **"nothing depends on this"** in `--ink-2` *instead of* the
+symbol/file counts, which stay in the side panel. The island verdict is computed from the whole link set, so hiding test modules
+cannot manufacture one. Selecting the module adds a sentence in the panel. Note the box is sized from whichever string it will
+show, so the layout and the node must be given the same verdict.
+
+**Generated files recede everywhere** (`files.generated`, §2.6): a module whose files are *all* tool-generated draws in
+`--ink-4` with a `--rule-soft` stroke; a generated file in the Map panel's file list, a generated group on the dead code list,
+a generated result in the search palette and a generated file's title in the File view are all `--ink-4`. Partly-generated
+modules are not dimmed — a module with one `.pb.go` in it is still one somebody writes by hand.
+
+**What the list refuses to claim** is the whole design. Behind it, `src/graph/dead-code.ts` starts from "no incoming edge
+other than `contains`" and subtracts every candidate there is any reason to believe something reaches: exported symbols and
+header declarations, test and generated files, abstract and interface members, anything carrying a `decorates` edge, overrides
+of an ancestor's member, names the language calls by itself, vendored directories, files nothing in the index reaches (those are
+islands — the Map's job, not this list's), names the resolver failed to resolve somewhere, names shared with a symbol that IS
+referenced, and — the only rule that reads a file — names written more than once in a file that can reach them.
+
 ## 4. Libraries and versions
 - Svelte 5 (≥ 5.25) + Vite (workspace `ui/`), Svelte Flow `@xyflow/svelte` ^1.6 for the Map and Flow canvases only (custom nodes/edges,
   hidden handles for port spreading, local selection state — the pattern in docker-app's `StackGraph.svelte`); `@dagrejs/dagre` only as a