feat(ui): the Flow strip — how one symbol reaches another, one card per hop (CG-50)

Ask "how does execute reach getFile" in the search box and the viewer draws the
call path between them, left to right, opening every card at the exact line that
makes the next call. Dynamic-dispatch hops are dashed and name the site they
were wired at; "Read as flow" turns a trail walked by hand into the same strip.

The path finder is NOT new. `codegraph_explore` already leads its answers with
the longest call chain among the symbols an agent named, and a viewer that drew
a different path would get the two quoted against each other in a review. So the
search moved out of `ToolHandler` into `src/graph/named-symbol-flow.ts` and both
callers ride it — same tokens, same overload rules, same synthesized edges. What
stayed behind in `tools.ts` is the prose.

A pinned from/to question is the same search with two options changed, because
both ends being named is the evidence explore's one-unnamed-bridge cap stands in
for: it bridges freely, keeps twelve candidates per endpoint instead of six
(the CLI's own `main` sorts seventh of ten), and searches from both ends at once
— identical paths to the one-way walk on twelve measured pairs, 3-6x faster.

`/api/flow` is deliberately the one endpoint with no cache: its cards carry
source read from disk, and a drift verdict changes without the index changing.

Verified on this repo (`execute` to `rowToFileRecord`, 8 hops; `main` to
`resolveOne`, 7) and on a fresh excalidraw index, where `mutateElement` to
`renderStaticScene` crosses callback, react-render and jsx-child hops and lists
exactly the hops `codegraph_explore` prints.

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

README.md

@@ -346,6 +346,8 @@ What you get on that screen:
 - **Honest edges.** A guess CodeGraph isn't sure about is folded away as "uncertain" rather than shown as fact, and a symbol no test reaches within three hops says so.
 - **Search** (`/` or ⌘K) over every symbol and file, **entry points** to start from (routes, hubs, files that run code at import time), and a **trail** of the path you walked that lives in the URL, so you can send someone the exact route you took.
 - Click any file path to open the **file view**: everything that file depends on, its outline in source order, and everything that depends on it.
+- **Ask for a path.** Type "how does execute reach getFile" (or `execute -> getFile`) and you get the **flow**: one card per hop, each opened at the line that makes the next call. Hops that no static edge records — a callback, an interface dispatch, a React re-render — are drawn dashed and name where the handler was wired. "Read as flow" turns a walk you did by hand into the same strip.
+- **The map**: the whole project at module granularity, laid out from the graph with dependencies pointing down — never drawn by hand, and the same picture every time. Cycles are listed rather than straightened away.
 
 Options: `--port <n>` to pin a port (without it the viewer takes 4747, or the next free one),
 `--no-open` to just print the URL for a headless box or an SSH session, and