chore(prompt): trim performance-neutral stage operating-guidance block

Vikunja #169 audition result. The 5x5 controlled A/B
(docs/qa/QA-stage-prompt-audition-results-2026-07-16.md) found the curated
guidance block performance-neutral: 5/5 build success both variants, cost
differences within heavy-tailed noise. Trimmed to the single sentence the
gates don't already enforce (scaffolding-scope boundary); dropped the
read-before-write / verify-before-complete / use-exact-feedback nudges that
restate gate-enforced behavior. ON run 3 proved prose doesn't stop failure
loops — deterministic defenses do (filed Vikunja #191/#192, unblocked #78).

core/kernel/src/main/kotlin/com/correx/core/kernel/orchestration/DefaultSessionOrchestrator.kt

@@ -76,11 +76,15 @@ internal val GATE_REQUIRED_CAPABILITY: Map<String, String> = mapOf(
     WORKSPACE_PRECONDITION_GATE to "file_write",
 )
 
+// ponytail: trimmed to the single non-redundant sentence after the 2026-07-16 audition
+// (docs/qa/QA-stage-prompt-audition-results-2026-07-16.md) found the full block performance-neutral —
+// the read-before-write / verify-before-complete / use-exact-feedback nudges just restate behavior the
+// gates already enforce, and run 3 proved prose doesn't stop failure loops (deterministic defenses do).
+// Only the scaffolding-scope boundary encodes a decision no gate makes. Delete outright if a future
+// multi-fixture audit still shows no clarity value.
 internal const val CURATED_STAGE_OPERATING_GUIDANCE = """## Operating guidance
-Verify the current workspace before declaring completion. Read before modifying existing files.
 When the authoritative intent plainly requires project setup, creating its manifest, configuration,
-or entry file is in scope; do not spend turns re-deciding that settled boundary. Re-observe facts
-instead of assuming them, and use the exact gate/tool feedback to make the smallest effective fix."""
+or entry file is in scope; do not spend turns re-deciding that settled boundary."""
 
 // Deterministic failure category from the gate id (no LLM — keeps routing off the untrusted path).
 internal fun ticketCategory(gate: String): String = when (gate) {