phase29ap(p6): extend pattern2 plan subsets for stdlib

docs/development/current/main/phases/phase-29ap/README.md

@@ -57,12 +57,30 @@ Gate (SSOT):
 
 - Scope:
   - Remove Pattern8 from `LOOP_PATTERNS` so plan/composer stays SSOT for normal loops.
-  - Keep legacy table as last resort for Pattern2/4/9 only.
+  - Keep legacy table as last resort for Pattern6_NestedLoopMinimal / Pattern4 / Pattern9 only.
 - Guardrails:
   - No change to logs or error strings.
   - Legacy routing remains a last-resort fallback.
 
+## P5: Remove Pattern2 from JoinIR legacy table ✅
+
+- Scope:
+  - Remove Pattern2 (with break) from `LOOP_PATTERNS`.
+  - Keep plan/composer as the only routing path for Pattern2.
+- Guardrails:
+  - No change to logs or error strings.
+  - Fallback remains `Ok(None)` for non-matching plan cases.
+
+## P6: stdlib trim_start/trim_end subset (Pattern2BreakFacts) ✅
+
+- Scope:
+  - Add a conservative Pattern2BreakFacts subset for `trim_start`/`trim_end`.
+  - Normalize `not is_whitespace(...)` into `is_whitespace(...) == false` in facts.
+  - Restore quick smoke by ensuring stdlib loops are handled by plan/composer.
+- Guardrails:
+  - No new logs or error strings.
+  - Subset only: if shape deviates, return `Ok(None)`.
+
 ## Next (planned)
 
-- P5: Router pattern-name branching reduction (planner outcome + composer SSOT)
-- P6: Facts/Feature expansion if needed
+- P7: Legacy table shrink (Pattern9 removal) or leave as-is with justification