docs: terminal file viewer structure and capability census

Add CLAUDE.md structure notes for the viewer/ frontend and file_viewer/
backend, plus a Key Conventions reminder that a new local window needs its
own capability file and lib.rs's on_window_event guard. Extend default.json's
threat-model census to name file-viewer.json and its allow-destroy grant.

Tighten the capability test in file_viewer/mod.rs from a substring check to
a parsed serde_json assertion of the exact windows list and permission set
for both capability files, per Task 12's controller ruling.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -73,6 +73,12 @@ docker exec stdout → tokio task → emit("terminal-output-{sessionId}") → li
 - **`hooks/`** — All Tauri IPC calls are encapsulated in hooks (`useTerminal`, `useProjects`, `useDocker`, `useSettings`)
 - **`lib/tauri-commands.ts`** — Typed `invoke()` wrappers; TypeScript types in `lib/types.ts` must match Rust models
 - **`components/terminal/TerminalView.tsx`** — xterm.js integration with WebGL rendering, URL detection for OAuth flow
+- **`viewer/`** — the terminal file viewer's window (second Vite entry `viewer.html` →
+  `src/viewer/main.tsx`; CodeMirror 6). `lib/filePathLinks.ts` decides what a path is;
+  `components/terminal/filePathLinkProvider.ts` registers it with xterm. The OSC 8 handler now
+  runs with `allowNonHttpProtocols` on and dispatches `file:` to the viewer, so every other scheme
+  must be refused *there*. `viewer.html` must never carry an inline `<style>` — Tauri would add a
+  style nonce and CodeMirror's injected styles would stop applying.
 - **`components/layout/`** — TopBar, MainTabs (the unified tab strip), Sidebar, StatusBar
 - **`components/projects/`** — `ProjectRow` (select-only list row), `ProjectList`, `AddProjectDialog`,
   and the editors reused by Project Home
@@ -161,6 +167,13 @@ docker exec stdout → tokio task → emit("terminal-output-{sessionId}") → li
   Beyond docker/project/settings/terminal: `inspect_commands.rs` (read-only views into a
   container — Claude sessions, installed capabilities, scheduler tasks), `auth_bridge_commands.rs`,
   `auth_token_commands.rs`.
+- **`file_viewer/`** — one window per click (`file-viewer-<n>`), a managed `ViewerRegistry`,
+  resolution by probing `/workspace/<p>` then `/workspace/<mount>/<p>` in one exec as `claude`,
+  polling by `sha256sum`, saves staged in `/tmp` and swapped in by a `sh` script as the container
+  user (spec §5 says why the archive API never writes to the target directory). Commands take
+  `window: tauri::Window`, gate on the label and act on the caller's own registry entry — no
+  viewer command accepts a path. The residual risk that any local window can call any app command
+  is deliberate and documented; the AppManifest lockdown spec closes it.
 - **`auth_bridge/`** — Host-side loopback bridge so browser logins run *inside* a container can
   complete against the host browser. Discovers listeners by parsing `/proc/net/tcp{,6}` (the image
   has no `ss`/`netstat`/`lsof`), binds host `127.0.0.1` **only**, and tunnels in over the Docker
@@ -601,6 +614,8 @@ Anthropic and Bedrock deliberately keep Claude Code's own defaults.
   `#[serde(default)]` on a `bool` yields `false`; follow the `default_full_permissions` pattern in
   `models/project.rs` for anything that should default to true.
 - Cross-platform paths: Docker socket is `/var/run/docker.sock` on Linux/macOS, `//./pipe/docker_engine` on Windows
+- A new local window needs its own capability file (`capabilities/file-viewer.json` is the
+  model), and `lib.rs`'s `on_window_event` stays guarded on `label() == "main"`.
 
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