skill: make the sh-vs-ps1 dispatch rule explicit

'Use whichever your host can launch' left the selection order implicit and
did not distinguish the two failure kinds. Now stated: dispatch on launcher
availability (not OS) — sh first, ps1 only when the sh launcher itself is
missing; and a STATUS=refuse from either entry point is final, never a cue
to try the other one for a different answer. The CI byte-diff exists
precisely so there is no different answer.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.agents/skills/peltier/SKILL.md

@@ -34,8 +34,12 @@ plugin, or copied into another project):
     powershell -NoProfile -ExecutionPolicy Bypass -File <skill-dir>/scripts/preflight.ps1
 
 The two entry points implement one contract and are byte-diffed against each
-other in CI — same checks, same output, same refusals. Use whichever your
+other in CI — same checks, same output, same refusals. Dispatch on launcher
-host can launch; never both, never neither.
+availability, not OS: try `sh` first; if the **launcher itself** is missing
+(`sh: not found` — a launch failure, not a refusal), run the PowerShell entry
+point instead. A `STATUS=refuse` from either is **final**: never run the
+second entry point hoping for a different answer — they are kept
+byte-identical in CI precisely so there is no different answer.
 
 Some harnesses block script files inside skills, so your installation may
 carry no `scripts/` directory. The script still exists exactly once — in the

.agents/skills/peltier/references/verify.md

@@ -6,11 +6,15 @@ faster. Find out. Works on any pair of shell commands, in any language.
 ## 0. Preflight
 
     sh <skill-dir>/scripts/preflight.sh
-    # no POSIX shell (Windows-native harness)? same contract, CI-diffed against the sh version:
+    # `sh` launcher missing ("sh: not found" — a launch failure, NOT a refusal)?
+    # same contract, byte-diffed against the sh version in CI:
     powershell -NoProfile -ExecutionPolicy Bypass -File <skill-dir>/scripts/preflight.ps1
     # installation carries no scripts/ (script-blocking harness)? run from the checkout:
     sh "$PELTIER_HOME/.claude/skills/peltier/scripts/preflight.sh"
 
+A `STATUS=refuse` from either entry point is final — do not run the other one
+looking for a different answer.
+
 Read the `key=value` output; you need `BENCH_RUNNER` and `PIN_SUPPORTED`. A
 refusal ends the **claim**, not the work — report the reason verbatim and do
 not substitute another timing tool.

.claude/skills/peltier/SKILL.md

@@ -34,8 +34,12 @@ plugin, or copied into another project):
     powershell -NoProfile -ExecutionPolicy Bypass -File <skill-dir>/scripts/preflight.ps1
 
 The two entry points implement one contract and are byte-diffed against each
-other in CI — same checks, same output, same refusals. Use whichever your
+other in CI — same checks, same output, same refusals. Dispatch on launcher
-host can launch; never both, never neither.
+availability, not OS: try `sh` first; if the **launcher itself** is missing
+(`sh: not found` — a launch failure, not a refusal), run the PowerShell entry
+point instead. A `STATUS=refuse` from either is **final**: never run the
+second entry point hoping for a different answer — they are kept
+byte-identical in CI precisely so there is no different answer.
 
 Some harnesses block script files inside skills, so your installation may
 carry no `scripts/` directory. The script still exists exactly once — in the

.claude/skills/peltier/references/verify.md

@@ -6,11 +6,15 @@ faster. Find out. Works on any pair of shell commands, in any language.
 ## 0. Preflight
 
     sh <skill-dir>/scripts/preflight.sh
-    # no POSIX shell (Windows-native harness)? same contract, CI-diffed against the sh version:
+    # `sh` launcher missing ("sh: not found" — a launch failure, NOT a refusal)?
+    # same contract, byte-diffed against the sh version in CI:
     powershell -NoProfile -ExecutionPolicy Bypass -File <skill-dir>/scripts/preflight.ps1
     # installation carries no scripts/ (script-blocking harness)? run from the checkout:
     sh "$PELTIER_HOME/.claude/skills/peltier/scripts/preflight.sh"
 
+A `STATUS=refuse` from either entry point is final — do not run the other one
+looking for a different answer.
+
 Read the `key=value` output; you need `BENCH_RUNNER` and `PIN_SUPPORTED`. A
 refusal ends the **claim**, not the work — report the reason verbatim and do
 not substitute another timing tool.