feat(terminal): newline chord as registry data, plus a Key tester in Settings

capabilities.newline replaces choosing the Shift+Enter bytes in the send-key
route. Key tester shows the keydown/keypress/keyup a browser reports.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/config/cli-registry/schema.ts

@@ -377,6 +377,7 @@ const capabilitiesSchema = z
     privilegedEnvKeys: z.array(envName).max(8),
     gates: z.record(z.string(), z.object({ minVersion: z.string().max(20), failClosed: z.boolean() }).strict()),
     maxFrameBytes: z.number().int().positive().optional(),
+    newline: z.enum(['line-feed', 'esc-enter']).optional(),
     customModelInjection: z.discriminatedUnion('kind', [
       z
         .object({

src/config/cli-registry/stock.ts

@@ -620,6 +620,9 @@ const CODEX: CliEntry = {
     // `dangerouslyBypassApprovals` on the wire), so it is the one that would have caught a
     // regression; `schema.ts` now rejects a name that is not a declared param.
     privilegedParams: [{ param: 'bypassApprovals', clampTo: false }],
+    // Codex's composer ignores a bare line feed in some terminals (Windows browsers, #495); the
+    // Esc+Enter chord is the one its own Option+Enter uses.
+    newline: 'esc-enter',
     // Verified by hand against a real llama.cpp server. Written to an isolated CODEX_HOME
     // so the user's real ~/.codex/config.toml is never touched.
     customModelInjection: {

src/config/cli-registry/types.ts

@@ -90,6 +90,9 @@ export interface CliVariant {
   args: ArgSpec[];
 }
 
+/** The newline chord a CLI's composer reads as "insert a line break" (see `CliCapabilities.newline`). */
+export type NewlineSequence = 'line-feed' | 'esc-enter';
+
 export interface CliLaunch {
   params: Record<string, ParamSpec>;
   /**
@@ -511,6 +514,14 @@ export interface CliCapabilities {
   gates: Record<string, { minVersion: string; failClosed: boolean }>;
   /** Cap on a single terminal frame, when this CLI needs a tighter one than the default. */
   maxFrameBytes?: number;
+  /**
+   * The bytes the web UI types into this CLI's pane for Shift+Enter (the `send-key` route).
+   * `line-feed` (`0x0a`, also what Ctrl+Enter sends) is what Claude Code's Ink input and most TUIs
+   * read as "insert a newline"; `esc-enter` (`ESC` `CR`, the same chord as Option/Alt+Enter and
+   * the mobile ⌥Enter key) is for a TUI that ignores a bare line feed. Absent = `line-feed`.
+   * Data, not a branch on the CLI id, so supporting another CLI's quirk is one line here.
+   */
+  newline?: NewlineSequence;
   /**
    * How this CLI is pointed at a user-supplied custom OpenAI-compatible
    * endpoint (local, e.g. llama.cpp, or cloud, e.g. Azure AI Foundry) — the