Shift+Enter newline, OAuth URL truncation, and the auth bridge toggle

Three fixes that all land on the same journey: sign in, paste a prompt,
and have the terminal behave the way every other Claude Code host does.

Shift+Enter inserts a newline
-----------------------------
xterm.js does not consult `shiftKey` for Enter (`Keyboard.ts`, case 13),
so Shift+Enter was byte-identical to Enter and submitted the prompt.
Both terminals now send `\x1b\r` (ESC+CR) instead, which Claude Code
parses as return+meta — the same bytes its own `/terminal-setup` writes
into the VS Code, Cursor, Alacritty and Zed keymaps, so this is in-band
rather than a guess. Not `\n`: Claude Code accepts it, but a shell would
run the line, so the two session types would diverge. Bound in Claude
sessions only for that reason.

`entrypoint.sh` sets `shiftEnterKeyBindingInstalled` in `~/.claude.json`
so the CLI stops printing its "run /terminal-setup" tip. Purely
cosmetic — the decoding is unconditional either way.

Alt+Enter has always done the same thing (xterm ESC-prefixes on altKey)
and was simply never documented. It is now, along with the rest.

OAuth login URL truncation
--------------------------
Two producers wrote one toast slot, last-writer-wins. The OSC 7777 relay
delivers the URL base64-encoded and therefore exact; ~300 ms later the
screen-scraper's debounce fired and overwrote it with a truncated guess
at the same link — a URL that parses, points at the right host, and
authorises nothing. The user is the one who has to notice.

Why the scraper truncated: `ANSI_RE` strips OSC sequences wholesale,
including the OSC 8 hyperlink whose parameter carries the complete URL.
Claude Code slices the *visible* text of that hyperlink to the terminal
width while every emission carries the whole URL in its parameter. The
backend already knew this (`commands/auth_token_commands.rs`); the
frontend did not.

- `urlDetector` now reads OSC 8 targets out of the raw buffer before
  stripping, filtered by a port of `usable_sign_in_link`, and tags every
  candidate with its provenance.
- The prompt slot gained `supersedes`: better provenance always wins,
  worse never does, and between equals only a candidate that *extends*
  what is showing may replace it. That last rule is `extendsUrl`,
  factored out of `pickSignInUrl` rather than copied — same rule, same
  reason, one implementation.
- `flatten` splits on a bare `\r` as well as on `\r?\n`, so a
  `\r`-repainted TUI frame no longer inflates a line past the width and
  suppresses a join that should have happened; and the width is now
  sampled at `feed()` rather than read at `scan()`, so a resize inside
  the 300 ms debounce cannot reassemble 80-column text against a
  120-column rule.

Also corrects the comment claiming `acquire_claude_token` enables the
auth bridge. It deliberately does not, and the module comment in
`auth_token_commands.rs` explains at length why not.

The auth bridge toggle
----------------------
`setAuthBridgeEnabled` and `getAuthBridgeStatus` had zero call sites:
the Rust was complete, the IPC wrapper shipped, and there was nowhere to
click — so the docs told users to "enable the Auth Bridge" for a switch
that did not exist. `AuthBridgeRow` is that switch, in Config → Runtime.
It deliberately does not go through the tab's stopped-only save: the
dedicated command exists so the bridge can be flipped while a login is
hanging in a running container, which is the only moment anyone reaches
for it.

It also subscribes to `auth-bridge-changed`, which the poller has been
emitting to nobody — so a host port the bridge could not take was a
completely silent failure, indistinguishable from a login that hung.

`tunnel.rs` promotes the best-effort `::1` bind failure from debug to a
warning recorded on the port. Half-bound is the failure mode that looks
like success: the status says bridged, and a client that resolves
`localhost` to `::1` without falling back is still refused.

Finally, for a recognised Anthropic sign-in URL the toast now leads with
"In container" and demotes the host "Open". The callback listener is
inside the container, so the container-side browser closes the loop with
no host round trip and no auth bridge; the host button stays as the
fallback. Ordinary URLs are unchanged.

Tests: 402 frontend (was 359), 285 Rust (unchanged).

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

app/src-tauri/src/web_terminal/terminal.html

@@ -334,6 +334,9 @@
     autocomplete="off" autocorrect="off" autocapitalize="off" spellcheck="false"
     enterkeyhint="send" inputmode="text">
   <button class="key-btn" id="btnEnter">Enter</button>
+  <!-- A newline *without* submitting. There is no Shift on a phone keyboard,
+       so the chord the desktop app binds needs a key of its own here. -->
+  <button class="key-btn" id="btnNewline" title="Insert a newline without submitting (Shift+Enter)">&#8629;+</button>
   <button class="key-btn" id="btnTab">Tab</button>
   <button class="key-btn" id="btnCtrlC">^C</button>
 </div>
@@ -360,6 +363,7 @@
   const emptyState = document.getElementById('emptyState');
   const mobileInput = document.getElementById('mobileInput');
   const btnEnter = document.getElementById('btnEnter');
+  const btnNewline = document.getElementById('btnNewline');
   const btnTab = document.getElementById('btnTab');
   const btnCtrlC = document.getElementById('btnCtrlC');
   const scrollBottomBtn = document.getElementById('scrollBottomBtn');
@@ -647,6 +651,28 @@
       });
     });
 
+    // Shift+Enter inserts a newline in Claude Code's prompt instead of
+    // submitting it. xterm.js does not consult `shiftKey` for Enter, so
+    // without this Shift+Enter is byte-identical to Enter.
+    //
+    // `\x1b\r` — ESC then CR — is what Claude Code parses as `return` with
+    // meta, and it is the same sequence its own `/terminal-setup` installs for
+    // VS Code, Cursor, Alacritty and Zed. Do not "simplify" it to `\n`: that
+    // also works in Claude Code, but a shell would *run* the line, so the two
+    // session types would diverge. Claude sessions only, for that reason —
+    // `bash -l` has no readline binding for `\e\r`.
+    term.attachCustomKeyEventHandler(e => {
+      if (
+        e.type === 'keydown' && e.key === 'Enter' && e.shiftKey &&
+        !e.ctrlKey && !e.altKey && !e.metaKey && !e.isComposing &&
+        sessionType === 'claude'
+      ) {
+        sendTerminalInput('\x1b\r');
+        return false; // xterm must not also send a bare CR, which submits
+      }
+      return true;
+    });
+
     // Track scroll position for scroll-to-bottom button
     term.onScroll(() => updateScrollButton());
 
@@ -799,7 +825,11 @@
         sendTerminalInput(val);
         mobileInput.value = '';
       }
-      sendTerminalInput('\r');
+      // Shift+Enter is a newline, not a submit — same bytes, and the same
+      // reasoning, as the terminal's own key handler above. A hardware
+      // keyboard on a tablet is the only way to reach this; the phone case is
+      // the dedicated newline button beside Enter.
+      sendTerminalInput(e.shiftKey ? '\x1b\r' : '\r');
     } else if (e.key === 'Tab') {
       e.preventDefault();
       sendTerminalInput('\t');
@@ -807,6 +837,7 @@
   });
 
   btnEnter.onclick = () => { sendTerminalInput('\r'); mobileInput.focus(); };
+  btnNewline.onclick = () => { sendTerminalInput('\x1b\r'); mobileInput.focus(); };
   btnTab.onclick = () => { sendTerminalInput('\t'); mobileInput.focus(); };
   btnCtrlC.onclick = () => { sendTerminalInput('\x03'); mobileInput.focus(); };