docs: clear the last session-only references from the plan

3g was still written as "rewrite, not transplant" against a suite the
fleet never sees, and it cited a commit's method rather than a rule.
It now states the rule directly: start from the behavior inventory in
CUJ_STATUS.md section 2, one test per behavior, coverage as the gate.
The reference suite is described as what not to copy and why.

Also replaced the two remaining "three review waves" references, which
name history a fresh reader cannot resolve, with "the reference
implementation".

Co-authored-by: Isaac

designs/PR_REWRITE_PLAN.md

@@ -67,7 +67,7 @@
 
 **3f** **Gateway-inference gating → keep, as a wave-1 workstream (~900 src+tests).** It is Bryan's explicit product rule, and it holds the PR's only migration. The rule has two clauses. First, the Model row offers Smart Routing for a harness only when the host reports that **that harness's** family resolves its inference to the AI Gateway. Second, the Smart Routing harness row appears only when the host reports gateway inference for **both** the claude and the codex families, because the harness routes across both. A host that reports nothing counts as unknown, and unknown never hides the option.
 
-**3g** **Test rewrite, not test transplant (−~4,000–5,000 of 12,216).** The current tests grew fix by fix across three review waves. They pin intermediate states. They duplicate coverage across consolidated files. They also carry fixture scaffolding for deleted machinery. The fleet writes a fresh suite against the *final* behavior per area. The coverage-gated method from `f8328623` worked, so reuse it. This time start from the behavior list, not from the old files. **RESOLVED (7d): there is no numeric line target.** The goal is a directed, useful suite that pins the final behavior. The gate is coverage against the registry inventory (`CUJ_STATUS.md` §2), not a line count. Every keep-core behavior gets a test. Nothing gets a test only to reach a number. The suite shrinks because the intermediate-state tests go, and the size that falls out is the size.
+**3g** **Write a directed suite, and do not copy the reference suite (7d).** Start from the behavior inventory in `CUJ_STATUS.md` §2, and write one test per behavior the branch must hold. **No numeric line target governs this.** The gate is coverage against that inventory, and not a line count: every keep-core behavior gets a test, and nothing gets a test only to reach a number. The reference implementation's 12,216 lines of tests are not the model to follow. They grew one fix at a time, so they pin intermediate states that no longer exist, they duplicate coverage across files that were later merged, and they carry fixtures for machinery this plan does not build. The new suite is smaller because it never acquires those, and whatever size falls out of the inventory is the right size.
 
 **3h** **Web slimming (−~1,000 of 5,104).** 3b takes the banner, its availability plumbing, and their tests out of the tree for good. No banner code and no banner carve-out survives anywhere in the web layer. The dead-code deletions already happened in review. The remaining +488 in `NewChatDialog.tsx` is mostly the harness row, the gating, and the persistence, so keep it. The web commit also carries the 2e model-indicator fix. Recommendation: make no web cuts beyond what 3b implies.
 
@@ -89,7 +89,7 @@ The chain therefore has four steps: strip the prefix → match the catalog exact
 - A directed test suite instead of an accreted one: about 4,500.
 - No per-fix consolidation scar tissue: about 500.
 
-From-scratch code should land below any estimate that assumes assembly, because the fleet never writes the intermediate states that three review waves left behind. The coverage gate (3g) still wins over any size preference.
+From-scratch code should land below any estimate that assumes assembly, because the fleet never writes the intermediate states that the reference implementation accumulated. The coverage gate (3g) still wins over any size preference.
 
 **3k** **Pi is not a routed harness, for now (7e).** Smart-routing eligibility requires a gateway-backed family. That requirement includes the mid-session toggle on ChatPage (`isCostRoutingEligible`). `gateway_inference` reports only the claude and codex families, so pi leaves the routed set. This closes a real hole: a pi session could turn Smart Routing on and pass the gateway rule vacuously, because the rule never saw pi's family. Two consequences follow. The rewrite cuts the bar list (~137 lines plus plumbing), because pi was its only consumer. The branch adds no layered redirect, because main's wire-compat redirect function stays as main wrote it. The door stays open for later. This PR does no pi work.
 

designs/ROUTING_OVERVIEW.md

@@ -50,7 +50,7 @@
 
 **2m — The CLI layer.** Three commands take `--smart-routing`, and the CLI runs preflight, drives the create, and passes the routed model to the wrapper as a launch flag. Without it a CLI user must start every routed session in a browser. It spans `cli.py` (+505), `smart_routing_cli.py` (+394), and `cli_native.py` (+77). Fate: keep as wave-2 workstream 6, inside the single PR (plan `2d`, `5b`, `4b`). It sits behind the HTTP boundary, so it runs beside the create-path stream it depends on.
 
-**2n — The tests.** The branch adds +12,278 lines of Python and web tests. They accreted per fix over three review waves, so they pin intermediate states and duplicate coverage. Fate: rewrite against the final behavior rather than transplant (plan `3g`). No line target governs the rewrite. The gate is coverage against the registry inventory, and the suite is as large as directed, useful tests of the final behavior require.
+**2n — The tests.** The reference implementation carries +12,278 lines of Python and web tests. They accreted one fix at a time, so they pin intermediate states and duplicate coverage. Fate: write a directed suite against the behavior inventory instead of copying them (plan `3g`). No line target governs the rewrite. The gate is coverage against the registry inventory, and the suite is as large as directed, useful tests of the final behavior require.
 
 **2o — The docs.** Five design documents add +2,879 lines under `designs/`, and `REVIEW_FIXES.md` adds +367. They carry the plan, the walkthrough, the evidence registry, and the codex model-state protocol. Fate: **ride the branch, then leave it** (plan `3a`, `4k`, resolved 2026-08-02). They stay tracked while the PR is open, because Bryan reads them there. A final commit deletes them before the merge, so the merged diff carries no docs and no docs PR follows.