ci+docs: SG-0 net-shrink PR-body discipline (Director Risk 5)

.github/PULL_REQUEST_TEMPLATE.md

@@ -77,6 +77,34 @@ PR #810 §0); not as a one-off. Cite the program brief.
 
 - **Exactly one disposition** (delete path **or** census shrink with N→M **or** lane + cited ROADMAP row/link): ___
 
+## SG-0 net-shrink discipline (required when `sg0_census_test.rs` changes)
+
+<!--
+CI: `scripts/check-pr-sg0-net-shrink-discipline.sh` (`.github/workflows/ci.yml` `ci` job).
+
+When this PR edits `src/v3/compiler/tests/integration/sg0_census_test.rs`, the
+GitHub PR **description** must include a line starting exactly with
+`SG-0 hand-path delta:` followed by a signed net path delta for this PR's
+census edits (`0`, `+0`, `-3`, `+1`, …).
+
+If the delta is a **strict net add** (`+1`, `+2`, … — not `+0`), the
+description must also include a line containing `SG-0 pairing: (a)` **or**
+`(b)` **or** `(c)` with the rationale on that line or immediately after.
+Pairing classes: **(a)** same-PR retirements (removed paths named), **(b)**
+Director-budget citation (URL), **(c)** structural deferral + named follow-up
+dispatch.
+
+**Delete this entire section** if `sg0_census_test.rs` is untouched.
+
+Authority: ROADMAP.md bullet *SG-0 PR-window net-shrink discipline*.
+-->
+
+**CI reads raw PR description text.** The lines the gate matches must start at column 0 with `SG-0 hand-path delta:` and (when required) `SG-0 pairing:` — a leading markdown list marker (`- …`) or bold wrapper on the same line will **not** satisfy the checker. Paste the two lines below the checklist into the description body as plain text (you can keep the bullets as a personal reminder).
+
+- **Paste into PR description — `SG-0 hand-path delta:`** ___
+
+- **Paste into PR description — `SG-0 pairing:`** ___ (`n/a` unless delta is strict `+N`, `N>0`)
+
 ## Per-PR debt-paydown receipt (required for all PRs)
 
 <!--

.github/workflows/ci.yml

@@ -75,7 +75,23 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
         with:
-          fetch-depth: 1
+          # Full clone so `git diff origin/main...HEAD` sees every commit on the PR
+          # branch (shallow `fetch-depth: 1` misses earlier commits and can false-negative
+          # the SG-0 net-shrink discipline gate).
+          fetch-depth: 0
+
+      - name: Fetch main for PR discipline diffs
+        if: github.event_name == 'pull_request'
+        run: git fetch origin main:refs/remotes/origin/main
+
+      - name: SG-0 net-shrink PR-body discipline (self-test)
+        run: bash scripts/check-pr-sg0-net-shrink-discipline.sh --self-test
+
+      - name: SG-0 net-shrink PR-body discipline
+        if: github.event_name == 'pull_request'
+        env:
+          PR_BODY: ${{ github.event.pull_request.body }}
+        run: bash scripts/check-pr-sg0-net-shrink-discipline.sh
 
       - name: Fabrication sentinel ratchet (P0-C)
         run: bash scripts/check-fabrication-sentinels.sh

ROADMAP.md

@@ -174,6 +174,8 @@ Both land inside T-PB-A because dissolving the compiler-local surface forces bot
 
 **SG-0 ratchet split is structural.** The R1 split (T-PB-A owns non-test; T-PB-B owns test) is now mechanically checked by `sg0_census_test.rs`: `EXPECTED_HAND_AUTHORED_NON_TEST` plus `EXPECTED_HAND_AUTHORED_FRAGMENTS` form the T-PB-A sub-ratchet, while `EXPECTED_HAND_AUTHORED_TEST` forms the T-PB-B sub-ratchet. The total census still checks their union against the generated-file partition. `pb_hand_rust_at_shim_floor` / `pb_rust_tests_outside_residual_zero` predicates still need to name this partition once T-TestGen extensions support them.
 
+- **SG-0 PR-window net-shrink discipline (Director course-correction — Reflective Analysis Risk 5, 2026-05-05):** Any PR that edits `src/v3/compiler/tests/integration/sg0_census_test.rs` must carry machine-checkable lines in the GitHub PR **description**: `SG-0 hand-path delta: …` (signed net path change to `EXPECTED_HAND_AUTHORED_*` ∪ fragments for this PR) and, when that delta is a **strict net add** (`+N` for integer `N > 0`), `SG-0 pairing: (a)|(b)|(c)` naming **(a)** same-PR retirements listing removed paths, **(b)** Director-budget citation (issue/comment URL), or **(c)** structural deferral with named follow-up dispatch. CI enforces this pairing via `scripts/check-pr-sg0-net-shrink-discipline.sh` (see `.github/PULL_REQUEST_TEMPLATE.md`); that consumer **fail-closes** when `origin/main` is unavailable on `pull_request`, and class **(a)** evidence requires the literal `removed` plus a census-shaped path token (see script header). Process-side complement to the mechanical SG-0 census and to **Course Correction #4** (`BridgeLedgerZero` decreasing-open-count ratchet — R3 Verification; see ROADMAP Pattern E / course-correction #4 ~`:585`): that structural ratchet is owned separately; this rule works at PR cadence regardless of BridgeLedgerZero execution state.
+
 ### Relationship to existing milestone status
 
 R1 absorbs what was "Post-A/B Lane Plan" and L1.5 forward work, framed by release deliverable rather than architectural stage. The status table below stays accurate for backward-looking context; R1 is the forward-looking companion.