feat(ui): the whole file — full source with gutter ports and intra-file call arcs (CG-52)

The File view gains a Source tab: the file itself, top to bottom, with the
Symbol view's line grid, gutter ports and call-site links, a line-anchored
callee rail, and — in the left margin — an arc for every call that stays inside
the file, drawn from the calling line to the callee's definition line.

The arcs are the point. Source order is already a layout, chosen by whoever
wrote the file, so a file's internal call structure can be drawn with no
algorithm placing anything. Crabviz's idea, in the one place it is legible.

Everything is arithmetic, not measurement. The Symbol view queries the laid-out
DOM to place a callee row beside its line; a 6 820-line file cannot afford that.
Here a line is exactly 20px at `10 + (n - 1) x 20`, so ~90 line elements exist at
a time and the arcs, ports, rail rows and connectors are all functions of a line
number. `src/mcp/tools.ts` scrolls at a 16.6ms median frame.

- `GET /api/filecode/<path>` — outline, one call group per (caller, callee) PAIR
  with its call-site lines, unresolved references, and the file's length. The
  source is NOT in it: it pages through `/api/source` 800 lines at a time with a
  discarded 150-line lead-in, so a page starting inside a block comment does not
  render prose as code, and so the ports and arcs are complete from the first
  frame while the text fills in behind them.
- `intraFileCalls` is counted over the groups actually returned, so the header
  and the picture under it cannot disagree once a cap bites.
- Above 40 arcs the diagram narrows to the symbol under the pointer (or the one
  the scroll position is inside) and the header states the total. Accent is for
  the pointer only, never for the filter.
- Sticky outline rail at >= 1400px, following the reader down the file.
- `QueryBuilder.getUnresolvedReferencesInFile` — one indexed lookup instead of
  one per symbol; `buildOutlineEntries` lifted out of `/api/file` so both
  readings of a file draw the same rows.

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

CHANGELOG.md

@@ -32,6 +32,10 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
   The **"Read as flow"** button on the trail turns a walk you did by hand into the same strip. It is the same path finder `codegraph_explore` leads its answers with, so the picture and what your agent tells you can't disagree.
 
+- **Read a whole file, with its call graph in the margin, in `codegraph ui`.** The file screen gained a **Source** tab: the file itself, top to bottom, with the same gutter markers as the symbol view and the same right-hand list of what each line calls, positioned level with the line that calls it. A 6,800-line file scrolls at full speed — only the lines on screen are ever drawn, and the text pages in behind you while the markers are there from the first frame.
+
+  In the left margin is an arc for every call that stays inside the file, drawn from the calling line to the line the callee is defined on. Nothing is laid out by an algorithm — the author already put the symbols in order, so source order does the work, and this is the one place a file's internal call structure is legible at a glance. Hover a line to light the arcs the function under your cursor takes part in, and click an arc to jump to the other end. On a file with more than forty of them the picture narrows to the symbol you're reading instead of drawing a wash of overlapping sweeps, with the total in the header. A rail on the far left lists the file's symbols and follows you as you scroll, when the window is wide enough for it.
+
 
 ## [1.6.0] - 2026-08-26