feat(#2094): migrate Trae onto EoS imperative adapter + SOLO stage-metadata upgrade (ADR-1239)

Fold trae logic branches into descriptor-driven reads: skipSharedHooksInstall
gates (dropped && !isTrae), and the case 'trae' path-rewrite arm now computes
the self-alias from the descriptor-driven dirName (.trae). Dead isTrae bindings
removed from uninstall/writeManifest/finishInstall. trae's skills dispatch was
already descriptor-driven (converter-by-name). RUNTIME_CONTENT_DISPATCH.trae is
left as a runtime-keyed table registration (its regex/callback rewrites can't be
a byte-identical descriptor map — matches cursor/windsurf/cline). trae stays in
RUNTIME_FLAG_IDS: isTrae still gates the agents-converter selection (agents out
of scope; removal gated on the cross-runtime agents-dispatch migration).
Byte-identical golden parity for all 16 runtimes.

UPGRADE: SOLO stage/trigger metadata — emitted Trae SKILL.md now carries
stage: workflow (descriptor-gated via hostBehaviors.soloStageMetadata) so
Trae's SOLO Agent can auto-invoke GSD skills at the corresponding stage. Field
shape is best-effort/inferred (Trae publishes no formal schema). trae.json
golden regenerated.

Tests: trae-imperative-reference (adapter/axes/fail-closed shouldFlattenDispatch
+ no runtime==='trae' source-grep, isTrae exempted for agents) + trae-upgrades
(stage: workflow on installed SKILL.md, descriptor-gated). Matrix note +
changeset added.

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

docs/reference/host-integration-capability-matrix.md

@@ -538,6 +538,8 @@ Documentation gaps:
 - dispatch.maxDepth — no integer depth limit documented beyond one orchestrator level.
 - dispatch.subagentToolkit — docs say agents can be configured with 'callable MCP services and other capabilities' but do not state whether sub-agents receive a full vs. restricted tool set.
 
+**EoS migration status (#2094):** Migrated onto the imperative adapter — partially. Two `runtime === 'trae'` string-equality branches folded into descriptor-driven `runtime.hostBehaviors`: `skipSharedHooksInstall:true` gates the shared-hooks install (Trae has no hook surface: `hooksSurface: "none"`), and the `case 'trae'` global-config-dir path-rewrite's self-alias regex is now built off the descriptor's `dirName` rather than a hardcoded `~/.trae/` literal (byte-identical output). Skills dispatch was already descriptor-driven before this migration (`artifactLayout.skills.converter: "convertClaudeCommandToTraeSkill"`, resolved by converter name, not a runtime check). **Still runtime-keyed** (not folded by #2094, matching the same posture as cursor/windsurf/cline, pending a future cross-runtime content-dispatch consolidation): `RUNTIME_CONTENT_DISPATCH.trae` in `bin/install.js` — its `md`/`js` bodies are regex-callback rewrites that cannot be reduced to a byte-identical descriptor map; and the `case 'trae':` switch arm itself in `src/runtime-artifact-conversion.cts` — the arm's *structure* (not just its self-alias regex) is boilerplate shared verbatim across 7 runtimes (`codex`, `cline`, `cursor`, `windsurf`, `augment`, `trae`, `codebuddy`) and remains a runtime-keyed `switch`. `trae` also remains in `RUNTIME_FLAG_IDS` (and `isTrae` remains in `bin/install.js`, gating only the agents-converter dispatch) pending the cross-runtime agents-converter dispatch migration — agents conversion is out of scope for #2094. One upgrade lands: **SOLO stage/trigger metadata** — every emitted `SKILL.md` now carries a `stage: workflow` frontmatter line (`runtime.hostBehaviors.soloStageMetadata`), so Trae's SOLO Agent can recognize GSD skills as workflow-stage skills for auto-invocation instead of requiring manual triggering; cite https://docs.trae.ai/ide/agent ("Agents in Trae can be called individually, or automatically called by SOLO Agent at the corresponding stage"). The field is a single fixed, best-effort/inferred GSD-side value — Trae's thin SPA docs don't publish a formal stage-metadata schema. The four `undocumented` dispatch sub-axes (`nested`, `maxDepth`, `subagentToolkit`, `backgroundDispatch`) keep dispatch flattened (`shouldFlattenDispatch` fails closed to inline) — fail-closed negotiation, not a regression.
+
 ---
 
 ## kimi