feat(agent-presets): give a preset a name and a description

A picker showed directory names, so the settings page could only ever list
`standard` / `core-web` / `cordis` and hope the reader knew what they meant.
A preset may now publish display text in an optional `preset.yml` beside
its composition, and the section renders cards — name, description, and the
one in use — instead of rows.

The file carries display text ONLY. `id` is the directory name and `trust`
comes from the root a preset was discovered under, so neither is writable
there: otherwise a locally authored preset could name itself into the
shipped set. It is a separate file because a composition is a top-level list
of plugin rows — YAML cannot carry sibling keys beside it, and a fake
metadata row would hand the Loader something to load.

Every read failure degrades to no metadata; absent, malformed, wrongly
typed, and blank all mean the same thing and the picker falls back to the
id. Presentation is not capability: a preset whose name is broken still
mounts.

The editor gained name and description fields above the YAML, and clearing
both removes the file rather than storing a blank name.

packages/preset/agent-presets/src/authoring.ts

@@ -14,6 +14,7 @@ import { entryListSchema } from '@cordisjs/plugin-include'
 import { writeFileAtomic } from '@deepseek-ai/dsh-atomic-write'
 import { expandHomePath } from '@deepseek-ai/dsh-paths'
 import { COMPOSITION_FILE } from './discovery.ts'
+import { METADATA_FILE, renderPresetMetadata, type PresetMetadata } from './metadata.ts'
 import type { AgentPreset, PresetRoot } from './types.ts'
 
 /**
@@ -111,6 +112,7 @@ export async function readComposition(preset: AgentPreset): Promise<string> {
  * @param roots - the configured roots; the first `user` one receives the write.
  * @param id - the preset id, which becomes its directory name.
  * @param content - the composition text.
+ * @param metadata - display name and description; clearing both removes the file.
  * @returns the absolute path written.
  * @throws when the id is unusable, the content is not an entry list, or the
  * deployment has no writable root.
@@ -119,6 +121,7 @@ export async function writeComposition(
   roots: readonly PresetRoot[],
   id: string,
   content: string,
+  metadata: PresetMetadata = {},
 ): Promise<string> {
   if (!PRESET_ID.test(id)) throw new InvalidPresetIdError(id)
   assertComposition(content)
@@ -127,6 +130,16 @@ export async function writeComposition(
   // Owner-only: a composition names the plugins a session runs, so it carries
   // the same weight as the settings document beside it.
   await writeFileAtomic(path, content, { mode: 0o600, dirMode: 0o700 })
+  // Display text lands after the composition, and only when there is any: a
+  // preset with no name should carry no metadata file rather than an empty
+  // one. Clearing both fields therefore removes the file.
+  const rendered = renderPresetMetadata(metadata)
+  const metadataPath = join(dir, METADATA_FILE)
+  if (rendered === undefined) {
+    await rm(metadataPath, { force: true })
+  } else {
+    await writeFileAtomic(metadataPath, rendered, { mode: 0o600, dirMode: 0o700 })
+  }
   return path
 }