Emit plugin logo/icon into host manifests that support it (Cursor plugin.json 'logo')

[ScriptedAlchemy]

Gap

Cursor's local plugin manifest schema supports a logo field, but agent-bundle provides no way to declare or emit one: defineConfig({ plugin: ... }) has no logo/icon field, and cursorManifest() emits only name, displayName, description, version, hooks, mcpServers, skills, and variables. The assets mechanism can copy an image into the artifact but cannot populate the manifest reference.

Observed while shipping cargo-hauler's branding (https://github.com/ScriptedAlchemy/cargo-hauler — docs/media/logo.png exists, host UI cannot show it).

Ask

• Add an optional plugin.logo (path) to config; validate the file exists at build time.
• Emit it per target where supported: Cursor .cursor-plugin/plugin.json logo (copy the asset into the artifact and reference relatively). Claude/Codex manifests currently have no icon field — skip until they do.
• Conformance coverage per Adopt pinned schemas and ecosystem validators for generated plugin conformance (build-time + doctor) #133: pinned-schema fixture including the logo field, plus the staged-install path check from Generated plugin contract matrix: catch source→artifact→dev→installed-host drift before release #218 (manifest-declared logo path must resolve inside the deploy tree).

[ScriptedAlchemy]

Delivered in #267 (merge 738b14b).

• plugin.logo is an optional project-relative path; declaring one that is missing, empty, a directory, or outside the project root fails source validation with the new AB4012 error.
• Cursor emission per the ask: the image is copied into the artifact at assets/<project-relative path> and .cursor-plugin/plugin.json gains "logo": "./assets/…" — on both the single-host cursor target and the multi-host plugin bundle (one shared copy).
• Honest omission: Claude/Codex manifests emit no logo/icon field; tests pin that on both surfaces, and their pinned schemas remain additionalProperties: false.
• Conformance per Adopt pinned schemas and ecosystem validators for generated plugin conformance (build-time + doctor) #133: the pinned Cursor plugin schema already declares logo (relative path or absolute URL) — asserted in adapter-metadata.test.ts, so schema provenance is unchanged.
• Staged-install check per Generated plugin contract matrix: catch source→artifact→dev→installed-host drift before release #218: the installed-Cursor proof now asserts the manifest-declared logo path resolves inside the deploy tree and exists there; artifact validation independently fails with AB6025 when a manifest logo is missing from the artifact or escapes the deploy tree.

cargo-hauler's docs/media/logo.png case now works by declaring plugin: { logo: './docs/media/logo.png' }.

[ScriptedAlchemy]

Closed-issue audit (lane G1): VERIFIED, plus one proof-drift repair

Re-verified on origin/main (af1c18551 → a0562e6f4):

• plugin.logo optional project-relative path, AB4012 on missing/empty/dir/outside-root (packages/agent-bundle/src/config/validate.ts:761; docs/diagnostics.md:14).
• Cursor emission: .cursor-plugin/plugin.json logo: './assets/…' on both cursor and plugin targets (src/adapters/cursor.ts:266,417); pinned Cursor schema declares logo (src/adapters/schemas/cursor/plugin.schema.json:55, asserted in adapter-metadata.test.ts:219).
• AB6025 artifact validation (src/build/validate-artifact-logo.ts, docs/diagnostics.md:27); installed-Cursor proof asserts the manifest logo resolves inside the deploy tree (tests/support/host-install.ts:1021-1025).
• Tests run green in a fresh worktree: plugin-logo.test.ts, adapter-metadata.test.ts, artifact-validator.test.ts, host-install-proof.test.ts (Cursor + Codex + Claude legs, binaries present).

One later drift found and fixed: #364 extended logo emission to Codex (interface.logo) — beyond this issue's "skip Claude/Codex until they support it" — but did not update the binary-gated Codex install proof, so host-install-proof.test.ts :: installs through Codex was red for anyone with codex installed (interfaceFields expectation missing logo). Repaired in #366 (a0562e6f46be94910f181499cc3b4c364d00937c); Codex proof 1/1 green locally against codex-cli 0.147.0. Leaving closed.