fix(#1521): resolve own runtime + worktrees-off for all non-Claude installs (#1537)

* fix(#1521): resolve own runtime + worktrees-off for all non-Claude installs

Generalizes the Codex-only #1515/#1519 fix to every non-Claude runtime, and
wires it into the real install path (where it was previously dead-on-arrival).

Root causes:
1. The runtime-default stamping lived only in `_applyRuntimeRewrites`, but the
   installer emits `gsd-core/workflows/*.md` via `copyWithPathReplacement`, which
   never calls it — so a real `--codex`/`--cursor`/etc. install emitted
   `--default claude` and worktrees-on. RUNTIME mis-resolved to claude and the
   workflow ran executors unisolated against the main checkout. (#1515/#1519 were
   also dead-on-arrival in real installs; this repairs them.)
2. Only `case 'codex'` was stamped; every other non-Claude runtime kept the
   Claude default.

Fix:
- New `_stampNonClaudeRuntimeDefaults(content, runtime)` (single shared helper)
  stamps `--default <runtime>` + `use_worktrees=false` for every `runtime !=
  claude`; called from both `_applyRuntimeRewrites` and, crucially,
  `copyWithPathReplacement` in bin/install.js (the real workflow emit path).
- Generalize the fail-closed worktree guard `= codex` -> `!= claude` in
  execute-phase/quick/diagnose-issues (worktree isolation is Claude-Code-only).
- Flip manager/autonomous inline-vs-background gating to `codex -> background,
  everything-else -> inline` (research: only Codex can background-nest the
  pipeline's subagents; all others run inline, which they support).

Worktree-capability determination is research-backed (official docs for all 14
non-Claude runtimes: none honor GSD's isolation="worktree" mechanism, only Codex
background-nests). New end-to-end real-install test asserts the EMITTED workflow
is stamped — the regression guard that would have caught the dead-on-arrival bug.

Closes #1521

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013vX5eUtWa2wsZEyeMf5i3r

* chore(#1521): backfill changeset PR number (#1537)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013vX5eUtWa2wsZEyeMf5i3r

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/runtime-artifact-conversion.cts

@@ -2119,6 +2119,40 @@ function computePathPrefix({ isGlobal, isOpencode, isWindowsHost: _isWindowsHost
   return `${resolvedTarget}/`;
 }
 
+/**
+ * Canonical list of every non-Claude runtime that gsd-core emits artifacts for.
+ * Exported so test files can import this single source of truth rather than
+ * maintaining divergent hand-rolled arrays (#1521).
+ *
+ * Keep in sync with the runtime flags in bin/install.js and getDirName().
+ */
+const NON_CLAUDE_RUNTIMES: string[] = [
+  'codex', 'opencode', 'kilo', 'gemini', 'copilot', 'antigravity',
+  'cursor', 'windsurf', 'augment', 'trae', 'qwen', 'hermes', 'kimi',
+  'codebuddy', 'cline',
+];
+
+/**
+ * #1521: Every non-Claude runtime resolves its own runtime identity from a
+ * runtime-neutral config, and defaults workflow.use_worktrees to false —
+ * GSD's worktree isolation uses Claude Code's isolation="worktree" spawn
+ * parameter, which no other runtime honors. Stamped into the emitted
+ * workflow runtime-resolution blocks. (Generalizes the Codex-only #1515 fix.)
+ *
+ * @private — exported as `_stampNonClaudeRuntimeDefaults` for tests.
+ */
+function _stampNonClaudeRuntimeDefaults(content: string, runtime: string): string {
+  content = content.replace(
+    /config-get workflow\.use_worktrees --raw 2>\/dev\/null \|\| echo "true"/g,
+    'config-get workflow.use_worktrees --default false --raw 2>/dev/null || echo "false"',
+  );
+  content = content.replace(
+    /config-get runtime --default claude --raw 2>\/dev\/null \|\| echo "claude"/g,
+    `config-get runtime --default ${runtime} --raw 2>/dev/null || echo "${runtime}"`,
+  );
+  return content;
+}
+
 /**
  * Apply the per-runtime rewrite table to a single content string.
  * Relocated from bin/install.js `_applyRuntimeRewrites`.
@@ -2133,26 +2167,20 @@ function _applyRuntimeRewrites(content, runtime, pathPrefix, isGlobal = false, a
   const dirName = getDirName(runtime);
   const normalizedPathPrefix = pathPrefix.replace(/\/$/, '');
 
+  // #1521: stamp runtime identity + use_worktrees=false for every non-Claude runtime
+  // before brand-specific path rewrites, so the replace operates on the pristine
+  // source line and is idempotent regardless of subsequent path substitutions.
+  if (runtime !== 'claude') {
+    content = _stampNonClaudeRuntimeDefaults(content, runtime);
+  }
+
   switch (runtime) {
     case 'codex':
       content = content.replace(/~\/\.claude\//g, pathPrefix);
       content = content.replace(/\$HOME\/\.claude\//g, pathPrefix);
       content = content.replace(/\.\/\.claude\//g, `./${dirName}/`);
       content = content.replace(/~\/\.codex\//g, pathPrefix);
-      // #1515: stamp Codex's own runtime identity + safe worktree default into
-      // emitted workflow runtime-resolution blocks. A Codex install with a
-      // runtime-neutral .planning/config.json must resolve RUNTIME=codex (Codex
-      // cannot honor Claude's isolation="worktree"), and default
-      // workflow.use_worktrees to false so the fail-closed guard lets execution
-      // proceed without worktrees instead of falling back to Claude semantics.
-      content = content.replace(
-        /config-get runtime --default claude --raw 2>\/dev\/null \|\| echo "claude"/g,
-        'config-get runtime --default codex --raw 2>/dev/null || echo "codex"',
-      );
-      content = content.replace(
-        /config-get workflow\.use_worktrees --raw 2>\/dev\/null \|\| echo "true"/g,
-        'config-get workflow.use_worktrees --default false --raw 2>/dev/null || echo "false"',
-      );
+      // #1515 stamp moved to _stampNonClaudeRuntimeDefaults (#1521 generalisation).
       content = processAttribution(content, attribution);
       break;
 
@@ -2531,4 +2559,7 @@ export = {
   rewriteStagedCommandBodies,
   _computePathPrefix: computePathPrefix,
   _applyRuntimeRewrites,
+  _stampNonClaudeRuntimeDefaults,
+  // #1521: canonical non-Claude runtime list for test files and tooling
+  NON_CLAUDE_RUNTIMES,
 };