chore(tasks): decompose wave 2 into implementation tasks

- w2-ssr-proof and w2-code-proof: the two consumer-shaped proofs,
  parallel by construction (own test binaries, own fixture modules
  per the wave-1 convention)
- w2-conformance-battery: the standing verification set, ordered
  after the proofs so it consolidates over the final wave-2 tree and
  absorbs any stop-and-book findings; folds the wave-1 gate's
  reminder (b) (wasm build standing, not ad-hoc)
- review-wave-2: the wave gate, depends on all three
- decomposition record added to docs/plans/implementation.md with
  the logistic-ordering rationale; wave-2 status flipped to
  decomposed

Verification: taskgraph validate (18 tasks valid); em-dash grep
clean on all changed files

docs/plans/implementation.md

@@ -1,7 +1,8 @@
 ---
 status: open
 last_updated: 2026-11-06 (created at the start of implementation;
-  wave 1 decomposed the same day)
+  wave 1 decomposed and its gate passed the same day; wave 2
+  decomposed immediately after)
 ---
 
 # alkgen: Implementation plan
@@ -84,7 +85,7 @@ Dependency logic in one line: core foundations (consumer-shaped proofs
 | Wave | Contents | Depends on | Status |
 |---|---|---|---|
 | [1](#wave-1-the-core) | The core: manifest landing (dep pins, alktype removal, feature graph); the public error model; registry construction (strict mode, escaper policy, typed registration, helper seam); the render entry point (two sinks); engine fixture doubles | none | decomposed |
-| [2](#wave-2-consumer-shaped-proofs) | The generality proofs on shipped code: the full ssr-shaped (posture-B) fixture through the public API; the code-shaped (posture-A/C) fixture with ordering and determinism invariants; the conformance battery (strict-mode matrix, error surface, two-sink correctness, wasm, feature matrix) | wave 1 | planned |
+| [2](#wave-2-consumer-shaped-proofs) | The generality proofs on shipped code: the full ssr-shaped (posture-B) fixture through the public API; the code-shaped (posture-A/C) fixture with ordering and determinism invariants; the conformance battery (strict-mode matrix, error surface, two-sink correctness, wasm, feature matrix) | wave 1 | decomposed |
 | [3](#wave-3-validation--release) | Release readiness (README, CHANGELOG, rustdoc, dry-run, freeze inventory); the release gate; the publish | waves 1 + 2 | planned |
 
 ## Wave 1: The core
@@ -233,6 +234,34 @@ falsifiability discipline).
 Wave 2 decomposes after the wave-1 gate, absorbing whatever it
 corrects.
 
+**Decomposition record** (2026-11-06, immediately after the wave-1
+gate passed green; that gate absorbed no corrections, so nothing above
+changes): wave 2 decomposes into three implementation tasks plus the
+gate under `tasks/implementation/`. Shape: `w2-ssr-proof` and
+`w2-code-proof` carry the two consumer-shaped proofs and are parallel
+by construction: each lives in its own test binary owning its fixture
+modules per the wave-1 convention, so there is nothing to sequence
+between them and no shared-module collisions. Then
+`w2-conformance-battery` depends on both proofs. The dependency line
+above reads proofs ∥ battery and the wave releases when both groups
+hold; the battery ordered after the proofs is a logistic choice with
+the wave-1 precedent (a chain is sequential *logistically*, not
+necessarily in working time): the battery consolidates the standing
+verification set over the final wave-2 tree (strict-mode matrix,
+error-surface rows, two-sink rows, feature-matrix posture, the wasm
+build joining the verification list), which is only meaningful once
+the proofs it stands beside have landed, and if a proof books a
+finding under the stop-and-book rule, the battery would order itself
+over the corrected surface rather than pin rows twice. Finally
+`review-wave-2` (the wave gate) depends on all three. Carried
+reminders from the wave-1 gate: (b) folds into the conformance task
+(the wasm build becomes a standing, unconditional entry in the
+verification command list rather than an ad-hoc gate run); (a) and
+(c) remain wave-3 concerns and are deliberately unassigned here. The
+stop-and-book rule applies throughout this wave: a proof that finds a
+needed core exception books it for the gate with written rationale
+and never silently absorbs it (ADR-001's falsifiability discipline).
+
 ## Wave 3: Validation & release
 
 - **Release readiness**: public-API rustdoc warning-free; README