feat(#778): cross-runtime command enrichment (Gemini {{args}}/!{}, Qwen priority) (#825)

* feat(#778): cross-runtime command enrichment (Gemini {{args}}/!{}, Qwen priority)

Enrich the installer's per-runtime command/skill generators with native,
verified, additive fields:

- Gemini CLI: map Claude's $ARGUMENTS -> Gemini's {{args}} in generated TOML
  commands so typed arguments interpolate; inject live .planning/STATE.md into
  /gsd:progress via a fixed, injection-safe !{cat .planning/STATE.md 2>/dev/null}
  shell block (no interpolated input).
- Qwen Code: emit the optional numeric `priority` field on main-loop skills so
  the most-used workflows sort first in the /skills list (higher = earlier per
  the Qwen skills spec; the issue's inverse numbering was corrected).

OpenCode per-command model/agent/subtask/variant enrichment was evaluated and
intentionally not implemented: `model` reintroduces the #1156
ProviderModelNotFoundError regression for non-Anthropic providers (the converter
deliberately strips model:), `subtask`/`agent` change execution semantics for
GSD's interactive commands, and `variant` is not in the OpenCode command schema.

Schemas verified against primary docs (Gemini custom-commands, Qwen skills,
OpenCode commands/skills). Adds tests/enh-778-* and how-to + USER-GUIDE docs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* chore(#778): set changeset PR number to 825

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

docs/USER-GUIDE.md

@@ -709,6 +709,15 @@ Both enrichments are written automatically at install time and require no manual
 
 See [Runtime-Aware Profiles](CONFIGURATION.md#runtime-aware-profiles-2517).
 
+#### Per-runtime command enrichment
+
+When generating artifacts, the installer adapts GSD commands to each runtime's native command schema:
+
+- **Gemini CLI** — generated TOML commands use Gemini's `{{args}}` placeholder (translated from Claude's `$ARGUMENTS`) so typed arguments interpolate into the prompt, and `/gsd:progress` injects live project state via a fixed `!{cat .planning/STATE.md 2>/dev/null}` shell block (no interpolated input, so no injection risk; Gemini shows its standard confirmation dialog).
+- **Qwen Code** — main-loop skills carry Qwen's numeric `priority` field so the most-used workflows (e.g. `new-project`, `plan-phase`, `execute-phase`) sort first in the `/skills` list; utility skills are left unset. Higher values sort earlier; the field affects only the `/skills` list order.
+
+See [How to install GSD Core on your runtime](how-to/install-on-your-runtime.md) for the full per-runtime details.
+
 ### Manual install / no-Node.js setup
 
 If you cannot run the GSD installer, you cannot use the source files in `agents/` directly — they are in Claude Code's native frontmatter format. For OpenCode, two transformations are required: