fix(pi): read the model off pi's footer so pi tabs and tiles name it

A pi session showed no model in its tab or tile unless one was passed at
launch, and none at all for the default route. pi draws its model in its
own footer, but its registry entry declared no modelDetect, so the pane
probe never read it.

The footer, from pi 1.1.0's footer code (0.84.4's is the same) and a live
pane (`0.8%/253k (auto)       qwen3.8-27b-pi • xhigh`): usage and context
on the left, then at least two spaces and `[(provider) ]<model>`, with
` • <thinking>` for a reasoning model and ` → <routed model>` when
routed. The last two rows are read (an extension status row can sit
below), and the context field picks the stats row out of them.

pi truncates the right side to fit a narrow pane with no ellipsis,
leaving exactly two spaces of padding. A name with nothing after it is
therefore read only with three or more spaces in front, and with two only
when a following ` •`/` →` proves it whole, so a cut-off name is never
shown. `no-model`, pi's placeholder, is rejected.

The read rides the idle confirmation pi gained with its workDetect entry.
Verified on an isolated instance: a fresh pi session published
qwen3.8-27b-pi (source screen) about 8 s after launch.

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

src/config/cli-registry/stock.ts

@@ -980,6 +980,23 @@ const PI: CliEntry = {
       promptGlyph: '─',
       workingLine: '── [⠋⠙⠹⠸⠼⠴⠦⠧⠇⠏] ',
     },
+    // pi's footer stats row, read from pi 1.1.0's footer code (0.84.4's is the same) and
+    // measured live as `0.8%/253k (auto)            qwen3.8-27b-pi • xhigh`: usage and
+    // context on the left, then at least two spaces and `[(provider) ]<model>` followed
+    // by ` • <thinking>` for a reasoning model and ` → <routed model>` when routed. Only
+    // the last two rows are read, which sit below the composer where the transcript never
+    // reaches (an extension's status row may sit under the stats row), and the context
+    // field (`12.3%/253k`, `?/128k`) picks the stats row out of them.
+    // ⚠️ A narrow pane truncates the right side with NO ellipsis, leaving exactly two
+    // spaces of padding. So a model with nothing after it is read only with 3+ spaces in
+    // front; with two, only when a following ` •`/` →` proves the name is whole (the
+    // bullet only ever follows a complete name, even when the cut lands right after it).
+    // A cut name is never shown. `no-model` is pi's placeholder when none is selected.
+    modelDetect: {
+      screenLine: String.raw`[%?]/[\d.]+[kKM]?(?: \(auto\))?(?: • xp)? {2}(?: +|(?=(?:\(\S{1,40}\) )?\S{1,80} [•→]))(?:\([\w.@-]{1,40}\) )?([A-Za-z0-9][\w.:/@+-]{0,79})(?= [•→]|\n|$)`,
+      screenLines: 2,
+      rejectWords: ['no-model'],
+    },
     // pi's absent-config default is an interactive trust PROMPT the session user could
     // just answer "yes" to, so omitting --approve is not itself a clamp — MATERIALIZE
     // approveProjectTrust:false so buildPiCommand emits --no-approve outright.