feat(codex): read Codex's own background-terminal row

Codex states background work too, and it says so in a different place. Claude
writes `· 1 monitor ·` on the last row of the screen; Codex pins
`1 background terminal running · /ps to view · /stop to close` ABOVE its
composer, which puts that row third from the bottom once the status line and
the composer are counted.

So how far up the screen to look is now per-CLI data as well:
`capabilities.workDetect.watchingLines`, bounded to 1..8 by the schema, and
defaulting to Claude's two. That bound is the point. The window is half the
injection guard, since every row it adds is another row the agent itself may be
able to write, and the label is what silences an idle alert. The other half is
the anchor, and Codex's is ` · /ps to view`: chrome naming a slash command only
the CLI can offer, so a session that writes "I left 1 background terminal
running for you" into its own output matches nothing.

Measured against a live codex-cli 0.154.0 pane rather than read out of a
binary. The row appears when the terminal starts, follows the composer down as
the conversation grows, and is gone after `/stop`. Verified end to end on an
isolated beta: the session payload carried `watching: "1 background terminal"`
and the badge rendered with it, and both cleared when the terminal stopped. The
fixtures in the tests are that capture verbatim.

Codex has no hook signals, so no idle prompt and no false NEEDS YOU row: for a
Codex session this is the badge alone, which is the case the maintainer said a
registry field could cover and a hook never could. Cross-CLI tests pin that
neither pattern fires on the other's screen, and that a CLI declaring nothing
still reports nothing.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/cli-registry.md

@@ -36,8 +36,8 @@ interface CliEntry {
   launch: CliLaunch; // the structured argv template
   env: CliEnv; // exports, tmux setenv keys, the env-override allowlist
   capabilities: CliCapabilities; // what every call site reads instead of the id
-  //   .workDetect?: { promptGlyph, workingLine, watchingLine? } — how this CLI's pane
-  //   shows work, and how it shows work it started in the background
+  //   .workDetect?: { promptGlyph, workingLine, watchingLine?, watchingLines? } — how
+  //   this CLI's pane shows work, and how it shows work it started in the background
   overlays: CliOverlays; // remote-SSH / Docker pane commands, credential store
 }
 ```
@@ -57,14 +57,24 @@ into `Session.watching`, and an idle prompt from such a session opens already ac
 so a pane waiting for its own background work never raises an alert a human cannot answer.
 Group 1 is the label, and a CLI that declares no pattern reports no background work.
 
+Two CLIs declare such a row today, and they put it in different places. Claude writes its
+chip on the last row of the screen, so it keeps the default window of `WATCHING_TAIL_LINES`
+rows and anchors on the `·` its footer joins items with. Codex pins
+`1 background terminal running · /ps to view · /stop to close` ABOVE its composer, which
+puts the row third from the bottom once the status line and the composer are counted, so its
+entry declares `watchingLines: 4` and anchors on the ` · /ps to view` tail. Both were
+measured against live panes rather than read out of a binary, which is the standard for
+adding a third.
+
 That label is the one value in the registry that an AGENT can influence, because it comes off
 the agent's own screen. Two things keep it honest, and both belong to whoever adds a pattern
-for a new CLI. `watchingLabel()` in `session-activity.ts` searches only the last
-`WATCHING_TAIL_LINES` rows, which is the part of the screen the CLI draws rather than the
-agent, and the pattern itself anchors on the separator that CLI's footer uses to join its
-items. Without both, an agent could silence its own idle alert by printing `· 1 monitor ·`
-into its output. The label is also ANSI-stripped and length-capped at the source, since it
-ends up on a badge and in an approval card.
+for a new CLI. `watchingLabel()` in `session-activity.ts` searches only the last few
+non-blank rows, which is the part of the screen the CLI draws rather than the agent, and the
+pattern anchors on chrome only that CLI can produce. Without both, an agent could silence its
+own idle alert by printing the words into its output. Keep the window as small as the layout
+allows, since every row it adds is another row the agent may be able to write. The label is
+also ANSI-stripped and length-capped at the source, since it ends up on a badge and in an
+approval card.
 
 ### Three capabilities that must stay independent