fix(#1520): randomize mktemp temp paths on BSD/macOS (XXXXXX must be path-final) (#1550)

* fix(#1520): randomize mktemp temp paths on BSD/macOS (XXXXXX must be path-final)

BSD/macOS mktemp only substitutes the XXXXXX template when it is the final
path component. Templates like `...-XXXXXX.json` / `gsd-pr-body.XXXXXX.md`
return a LITERAL `XXXXXX` path (no randomization) on macOS, so concurrent
workflow runs collide on the same temp manifest/body file — one run can
overwrite or consume another's. Reproduced on macOS: the second call to the
suffixed template fails `mkstemp: File exists`.

Fix: use a suffixless `XXXXXX` template (so it IS the final component), then
rename to add the intended extension — portable across BSD + GNU userlands,
no GNU-only `--suffix` flag. Empty-file-then-write semantics are preserved at
every site.

Affected workflow temp files:
- execute-phase.md: gsd-worktree-wave-*.json (wave worktree manifest)
- quick.md:         gsd-quick-worktree-*.json
- spec-phase.md:    edge-probe-reqs-*.json
- ship.md:          gsd-pr-body-*.md
- profile-user.md:  gsd-profile-answers-*.json, gsd-profile-analysis-*.json

The execute-phase.md edit uses a compact intermediate var + trailing comment
to stay under the ADR-857 phase-6 size ceiling (93166); regenerated the
workflow size baseline accordingly. Validated on macOS: 20 concurrent calls
yield 20 unique randomized paths.

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

* chore(#1520): add changeset fragment (Fixed)

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

* test(#1520): add fail-first workflow-prose guard for mktemp XXXXXX suffix

Repo-wide scan of gsd-core/workflows/**/*.md that fails on any mktemp
template whose XXXXXX run is followed by a filename suffix (the BSD/macOS
non-randomizing form). Fails on the six pre-fix instances and passes on
the fix, and locks the copy-paste-prone idiom out of future workflows.
Mirrors the bug-637 hardcoded-$HOME workflow guard.

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

* test(#1520): rename regression test to fix- prefix (regression-test-names lint)

New tests/bug-NNNN-*.test.cjs files are banned by the lint-regression-test-names
ratchet; use the fix- prefix (matches the fix-1445 precedent).

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

* test(#1520): add issue ref to allow-test-rule exemption (ADR-456 lint)

lint-allow-test-rule-refs requires every new `allow-test-rule:` comment to
carry a #NNN reference (don't allowlist). Add (#1520) to the source-text
exemption.

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

* fix(#1520): abort touched mktemp chains on failure (|| exit 1)

Per review: the VAR=$(mktemp …) && mv … && VAR=… chains dropped the issue's
suggested failure guard. If mktemp fails, $VAR is empty and the subsequent
mv/write lands on an unintended relative path. Add `|| exit 1` to all six
touched chains so a mktemp failure aborts the snippet. Regenerated the
workflow size baseline for the slightly longer lines.

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

* chore(#1520): rebase onto next — regen size baseline + describe rename

Resolve the workflow-size-baseline.json conflict from next advancing by
regenerating from the current workflow sizes. Also rename the test describe
from `bug #1520` to `#1520` (the file uses the fix- prefix) per review nit.

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

* fix(#1520): harmonize profile-user mktemp to ${TMPDIR:-/tmp} (review nit)

The two profile-user.md temp sites this PR already rewrites kept a hardcoded
/tmp while the four sibling workflows use ${TMPDIR:-/tmp}. Harmonize for
consistency and macOS-correctness (some sandboxes have no writable /tmp).
Regenerated the workflow size baseline.

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

* chore(#1520): regen size baseline after rebase onto next

---------

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

tests/workflow-size-baseline.json

@@ -24,7 +24,7 @@
   "docs-update.md": 55662,
   "edit-phase.md": 12883,
   "eval-review.md": 9923,
-  "execute-phase.md": 93426,
+  "execute-phase.md": 93517,
   "execute-plan.md": 32611,
   "explore.md": 10497,
   "extract-learnings.md": 12849,
@@ -56,9 +56,9 @@
   "plan-review-convergence.md": 23468,
   "plant-seed.md": 11741,
   "pr-branch.md": 15919,
-  "profile-user.md": 20650,
+  "profile-user.md": 21202,
   "progress.md": 30555,
-  "quick.md": 48830,
+  "quick.md": 49139,
   "reapply-patches.md": 20393,
   "remove-phase.md": 8469,
   "remove-workspace.md": 7507,
@@ -70,10 +70,10 @@
   "settings-advanced.md": 39666,
   "settings-integrations.md": 15848,
   "settings.md": 33413,
-  "ship.md": 24388,
+  "ship.md": 24647,
   "sketch-wrap-up.md": 14223,
   "sketch.md": 19960,
-  "spec-phase.md": 31503,
+  "spec-phase.md": 31752,
   "spike-wrap-up.md": 15092,
   "spike.md": 24517,
   "stats.md": 6718,