fix(#4011): key the TDD runtime gate on TDD_MODE alone (#4180)

* test(#4011): TDD gate keys on TDD_MODE alone, not the MVP intersection

Contract updates: no shipped line may conjoin MVP_MODE with TDD_MODE as
a gate condition, the end-of-phase escalation must not require MVP, the
executor agent's gate section triggers on TDD_MODE alone, and the gate
semantics reference loads without MVP_MODE.

* fix(#4011): key the TDD runtime gate on TDD_MODE alone

The RED-commit gate shipped as #76's MVP slice kept the paired
invocation's conjunct, so workflow.tdd_mode=true was silently inert on
every non-MVP phase, contradicting references/tdd.md's own contract.
Drops the MVP conjunct from the per-task gate and the end-of-phase
review escalation; rescopes execute-mvp-tdd.md's load condition,
gsd-executor's gate section, and mvp-concepts' intersection claim.
MVP remains free to imply TDD; the file is not renamed (stated
assumption in the PR body).

* test(#4011): scope no-conjunct detector to shell conditions; clean stale MVP+TDD phrasing

Review follow-ups: the detector now only inspects if/[ condition lines
so explanatory prose mentioning both flags cannot trip it; remaining
'under/outside MVP+TDD' phrases in execute-phase.md, the gate
reference, and docs/INVENTORY.md now describe TDD-mode semantics.

Emitted-Drift-Ack-Growth: execute-phase.md — TDD-gate decoupling comment + escalation rescoping (#4011)
Emitted-Drift-Ack-Growth: gsd-executor.md — gate section trigger rescoped to TDD_MODE alone (#4011)

* chore(#4011): backfill changeset pr number

---------

Co-authored-by: sim <sim@local>

gsd-core/workflows/execute-phase.md

@@ -194,15 +194,15 @@ Offer these recovery options:
 - `mark-and-skip` — record the anomaly and move on only with explicit confirmation.
 </step>
 
-**MVP+TDD gate.** Task-scoped enforcement runs inside plan execution (immediately before each implementation step), where `TASK_FILE`, `PLAN_ID`, and `TASK_ID` are defined. Keep the same predicate and RED-commit contract:
+**TDD gate.** Task-scoped enforcement runs inside plan execution (immediately before each implementation step), where `TASK_FILE`, `PLAN_ID`, and `TASK_ID` are defined. #4011: the gate keys on `TDD_MODE` ALONE — a discipline gate coupled to the product-scope `MVP_MODE` flag was silently inert on every non-MVP phase, contradicting `gsd-core/references/tdd.md`'s contract that `workflow.tdd_mode` binds for all `type: tdd` plans. MVP mode remains free to imply TDD; it is no longer required by it. Keep the same predicate and RED-commit contract:
 ```bash
-if [ "$MVP_MODE" = "true" ] && [ "$TDD_MODE" = "true" ]; then
+if [ "$TDD_MODE" = "true" ]; then
   IS_BEHAVIOR_ADDING=$(gsd_run query task.is-behavior-adding "$TASK_FILE" --pick is_behavior_adding)
   if [ "$IS_BEHAVIOR_ADDING" = "true" ]; then
     RED_COMMIT=$(git log --oneline --grep="^test(${PHASE_NUMBER}-${PLAN_ID}):" -- "**/*.test.*" "**/*.spec.*" "tests/" | head -1)
     if [ -z "$RED_COMMIT" ]; then
       gsd_run query state.update last_gate_trip "${PLAN_ID}/${TASK_ID}" || true
-      echo "MVP+TDD GATE TRIPPED: missing RED commit for ${PLAN_ID}/${TASK_ID}"
+      echo "TDD GATE TRIPPED: missing RED commit for ${PLAN_ID}/${TASK_ID}"
       exit 1
     fi
   fi
@@ -1245,16 +1245,16 @@ CHECK_EXIT=$?
 
 **Gate evaluation** uses the same two-step contract as `execute:wave:post` above.
 
-**TDD review escalation (overrides the advisory default for the `tdd.review-checkpoint` gate only).** The tdd `execute:post` gate is declared `blocking: false`, so by the generic contract above it displays its `message`/table and continues. There is ONE documented exception (see `~/.claude/gsd-core/references/execute-mvp-tdd.md`): when `MVP_MODE=true` AND `TDD_MODE=true` AND `GATE_RESULT.block == true` (one or more TDD plans miss a RED or GREEN gate commit), the end-of-phase TDD review escalates from advisory to **blocking under MVP+TDD** — refuse to mark the phase complete and present:
+**TDD review escalation (overrides the advisory default for the `tdd.review-checkpoint` gate only).** The tdd `execute:post` gate is declared `blocking: false`, so by the generic contract above it displays its `message`/table and continues. There is ONE documented exception (see `~/.claude/gsd-core/references/execute-mvp-tdd.md`): when `TDD_MODE=true` AND `GATE_RESULT.block == true` (one or more TDD plans miss a RED or GREEN gate commit; #4011 — no MVP condition), the end-of-phase TDD review escalates from advisory to **blocking under TDD** — refuse to mark the phase complete and present:
 
 ```
-Phase blocked: {N} TDD plan(s) violate the RED→GREEN gate sequence under MVP+TDD.
+Phase blocked: {N} TDD plan(s) violate the RED→GREEN gate sequence under TDD.
 Resolve and re-run /gsd execute-phase, or override with /gsd execute-phase {phase} --force-mvp-gate to ship anyway.
 ```
 
-(`--force-mvp-gate` is the documented, not-yet-implemented escape hatch.) Outside MVP+TDD, TDD-review violations remain advisory (table shown, execution continues).
+(`--force-mvp-gate` is the documented, not-yet-implemented escape hatch.) Outside TDD mode, TDD-review violations remain advisory (table shown, execution continues).
 
-**Proceed rule:** If `MVP_MODE && TDD_MODE && GATE_RESULT.block == true` for `tdd.review-checkpoint`: STOP — do NOT proceed to `close_parent_artifacts`, `regression_gate`, `verify_phase_goal`, or `phase.complete`. Otherwise proceed normally.
+**Proceed rule:** If `TDD_MODE && GATE_RESULT.block == true` for `tdd.review-checkpoint`: STOP — do NOT proceed to `close_parent_artifacts`, `regression_gate`, `verify_phase_goal`, or `phase.complete`. Otherwise proceed normally.
 </step>
 
 <!-- gsd:section id="gap-closure-artifacts" when="state:gap-closure-phase" -->