fix(web): clamp preset card descriptions instead of sizing the roster

A preset publishes its own description, of any length, and `.cards` sizes
rows with `grid-auto-rows: 1fr` — which makes every implicit row the same
height, not just the row holding the tall card. One long description
therefore set the height of the whole roster.

The description now clamps to four lines and offers the rest through the
shared Tooltip, attached only while the element actually overflows. Card
height stays derived: with the description bounded, `grid-auto-rows: 1fr`
already equalizes, and a card carrying the broken-preset reason or a
revealed path still sizes itself.

Tooltip gains an optional `maxWidth`; its default half-viewport cap
renders a description wider than the settings dialog it belongs to.

The failed-shape-check badge reads "Failed to load" rather than "Broken":
discovery reports a composition that is missing, unreadable, or malformed,
which overstates as damage.

Fixes #2238

packages/client/ui-agent-preset/README.md

@@ -36,6 +36,8 @@ A fourth surface, its own settings page (`settings.section` id `agent-presets`,
 
 The browser edits no composition text. Editing YAML in a web textarea was a weak surface (no completion, no highlighting, no diff), so a new preset is a host-side copy of an existing one — the dialog collects an id (it becomes the directory name, which is why it must be named up front and cannot change later) and an optional display name, and `{ from, id, name? }` is all that crosses the wire. Everything else — description, composition, skills — is edited in the preset's own files, and the page's other job is getting the user TO those files: the copy completes by opening the new directory, and every custom row keeps a location action. Where the host has no desktop opener (`hasDocument: false` on the roster; remote and container deployments), the same actions answer the directory as text on the row instead of offering a button that would spawn into nothing.
 
+A preset publishes its own description, of any length, and the grid sizes every card row alike — so an unbounded description would set the height of the whole roster. Cards clamp it to four lines and offer the rest in a tooltip, attached only while the text is actually cut off. The clamp is CSS, so the whole description stays in the accessibility tree whatever the card shows.
+
 A shipped preset opens in the read-only viewer. It is the known-good composition a copy starts from, so reading it is the point; it offers no location and no delete — its install is overwritten by upgrades and is not the user's to manage. The intro carries the guidance a create button used to imply: duplicate an existing preset and make it yours, or let the agent draft one in Creator mode.
 
 Beside copying sits the conversational entry: when the roster carries the self-referential `cordis` preset, a dashed add-card (the Models page's affordance) stages it and starts a new session — the section closes the settings panel through the shell's owner-prop `close` and the new-session chip's own applier composes the blank session the workspace flow produces. The seat keeps a late roster load from regressing the display: staged pick first, then the composition the current session already carries, then the deployment default.
@@ -44,7 +46,7 @@ The dialog mirrors the host's own containment rule (`[a-z0-9][a-z0-9-]*`) and re
 
 Deleting removes the preset directory. Sessions already composed from it keep running — a composition is mounted once at session creation and nothing re-reads the file.
 
-A roster row carrying `broken` (the host's shape check found the composition missing or unloadable) renders as a marked card: red border, a Broken badge, the reason verbatim, the body disabled — it cannot become the default — and duplication disabled, since a copy of a broken preset is another broken preset. A broken custom row keeps its location and delete actions, because the files are where it gets fixed and deleting is how a ghost directory (composition deleted by hand, directory still blocking the id) is cleared; a broken shipped row withholds the viewer too — there is no readable composition to show. The two pickers (the General row and the new-session chip) drop broken presets entirely: they choose the NEXT session's composition, and offering one that cannot compose would only defer the failure to the session start.
+A roster row carrying `broken` (the host's shape check found the composition missing or unloadable) renders as a marked card: red border, a "Failed to load" badge (what discovery observed, not a claim that the files are damaged — the usual cause is a composition the user just edited or deleted), the reason verbatim, the body disabled — it cannot become the default — and duplication disabled, since a copy of a broken preset is another broken preset. A broken custom row keeps its location and delete actions, because the files are where it gets fixed and deleting is how a ghost directory (composition deleted by hand, directory still blocking the id) is cleared; a broken shipped row withholds the viewer too — there is no readable composition to show. The two pickers (the General row and the new-session chip) drop broken presets entirely: they choose the NEXT session's composition, and offering one that cannot compose would only defer the failure to the session start.
 
 Setting the default writes the `agent-presets` settings namespace, which the host exposes to configuration clients ([`dsh-apiproxy`](../../host/apiproxy/README.md) keeps an explicit allowlist — a namespace outside it makes a picker move and then silently forget).