security: close capability, CSP and auth-bridge holes

capabilities/default.json
- Drop every `store:*` grant. `@tauri-apps/plugin-store` has no caller in
  `app/src`, and the plugin's `resolve_store_path` is a `PathBuf::push` against
  AppData — `push` discards the base for an absolute path, so the grant was an
  arbitrary host read/write from the webview.
- Replace `opener:default` with a scoped `opener:allow-open-url` (http/https
  only). That drops `reveal_item_in_dir`, which the plugin does not scope-check
  and nothing here calls, and the unused mailto:/tel: scope.
- Record the unscopable `drag:allow-start-drag` residual risk in `description`.

tauri.conf.json
- Add `form-action 'none'`, `base-uri 'none'`, `object-src 'none'`.
  `form-action` has no `default-src` fallback, so an injected auto-submitting
  form was unblocked even though `script-src 'self'` blocks XSS.
- Remove the dead `asset:` / `https://asset.localhost` img-src and `data:`
  font-src grants; `blob:` stays (the file viewer uses it).

auth_bridge
- The reserved-port set covered only this project's mappings and the two
  browser-view ranges. It now also covers the gateway, STT and web-terminal
  host ports (configured value and shipped default, read off the settings
  models) and every other project's published host port. A container binding
  container-loopback 4000 / 9876 / 7681 while those services were stopped had
  that port mirrored onto the host, unauthenticated, within one poll.
- Gate the host listener on fetch metadata: refuse a request that is a
  cross-site sub-resource, allow navigations (the OAuth redirect) and anything
  without `Sec-Fetch-*`. Non-HTTP connections are classified from their first
  line and forwarded verbatim. Residual risk is spelled out in the module docs.
- Bound the forwards: max concurrent connections per port, a first-byte
  deadline enforced before any `docker exec` is created, and an idle timeout.

browser_view/mod.rs
- `pick_viewer_port` reads procfs with `/usr/bin/cat`, not a bare `cat` the
  container can shim via its writable PATH entry.
- Treat port choice as check-then-bind: walk to the next free candidate when
  the viewer does not come up, instead of failing the start.

BrowserTab.tsx
- Sandbox the viewer iframe. Container-controlled content could `top.location`
  the app's webview away. `allow-top-navigation*` and
  `allow-popups-to-escape-sandbox` are deliberately absent.

HelpDialog.tsx
- Escape the quote characters in the entity pass and escape captured attribute
  values. `href="$2"` with `$2` = `[^)]+` let remote GitHub markdown close the
  attribute and open another, in a document rendered with
  `dangerouslySetInnerHTML`.

web_terminal/terminal.html
- SRI hashes plus `crossorigin` on the three jsdelivr bundles and the
  stylesheet, and a CSP for the page — it is served 0.0.0.0 behind a permissive
  CORS layer and nothing else gives it one.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GBq2rGum6GX7xXgsas1fDc

app/src-tauri/gen/schemas/capabilities.json

@@ -1 +1 @@
-{"default":{"identifier":"default","description":"Default capabilities for Triple-C","local":true,"windows":["main"],"permissions":["core:default","core:event:default","core:event:allow-emit","core:event:allow-listen","core:event:allow-unlisten","core:event:allow-emit-to","dialog:default","dialog:allow-open","dialog:allow-save","dialog:allow-message","dialog:allow-ask","dialog:allow-confirm","store:default","store:allow-get","store:allow-set","store:allow-delete","store:allow-keys","store:allow-values","store:allow-entries","store:allow-length","store:allow-load","store:allow-reset","store:allow-save","store:allow-clear","opener:default","opener:allow-open-url","drag:default","drag:allow-start-drag"]}}
+{"default":{"identifier":"default","description":"Default capabilities for Triple-C. Every entry here is an IPC command a compromised webview can call directly, so the set is kept to what the frontend actually uses. Two notes on what is deliberately absent and what is deliberately accepted: (1) the `store:*` grants were removed — nothing in `app/src` uses `@tauri-apps/plugin-store`, and the plugin's `resolve_store_path` is a `PathBuf::push` against AppData, which `push` discards outright when handed an absolute path, so the grant was an arbitrary host-file read/write primitive (`plugin:store|load` + `set` + `save` on `~/.claude/settings.json` is host code execution). (2) `drag:allow-start-drag` stays, and cannot be scoped — `tauri-plugin-drag` takes the item paths from the caller and has no scope mechanism, so a compromised webview could call `startDrag({ item: ['~/.ssh/id_rsa'] })` against any host path the user can read. It is not a silent exfiltration primitive: the drag only delivers anything if the user completes a real drop onto a real target, and the OS shows the drag under the cursor while it is in flight. Removing it would remove drag-out from the Files pane (`stage_container_file_for_drag`), whose fallback is the explicit \"Save to host…\" action. Accepted residual risk, recorded here rather than fixed.","local":true,"windows":["main"],"permissions":["core:default","core:event:default","core:event:allow-emit","core:event:allow-listen","core:event:allow-unlisten","core:event:allow-emit-to","dialog:default","dialog:allow-open","dialog:allow-save","dialog:allow-message","dialog:allow-ask","dialog:allow-confirm",{"identifier":"opener:allow-open-url","allow":[{"url":"http://*"},{"url":"https://*"}]},"drag:default","drag:allow-start-drag"]}}