chore(release): alkssh 0.2.0 — the sibling-adoption release

- version 0.2.0: the dep-req bumps (alkvault 0.2, alktunnels 0.5.0)
  are semver-significant for consumers; no alkssh public API change
  apart from what the bumps ripple through.
- CHANGELOG: the 0.2.0 entry (the three adoptions, the dropped wrap,
  the gate adoption, the harness fidelity fix, the new rows).
- tasks: record the w6-sibling-adoption wave (taskgraph validate:
  43 tasks).

Verification: scripts/matrix.sh green (exit 0 — the full suite per
feature build none/git/session/tunnel/sftp/--all-features + clippy x2
+ fmt + doc), cargo test --manifest-path fuzz/shared/Cargo.toml (11,
corpus replay), cargo publish --dry-run --allow-dirty (76 files,
342.6 KiB compressed).

tasks/implementation/w6-sibling-adoption.md

@@ -0,0 +1,51 @@
+---
+id: w6-sibling-adoption
+name: Wave 6 — the sibling-adoption wave (alkvault 0.2 + alktunnels 0.5.0 gate + alktty 0.8.2 docs)
+status: completed
+depends_on: [w5-publish]
+scope: moderate
+risk: medium
+impact: component
+level: implementation
+---
+
+## Description
+
+The three alkssh-filed upstream reviews all shipped: alkvault 0.2.0
+(review 001, the decrypt plaintext window), alktunnels 0.5.0 (review
+003 W1 absorbed in-repo; W2 is this adoption wave), alktty 0.8.2
+(review 004, the PTY exit-signal fidelity fix; docs-only adoption
+here). Adopt all three and publish as alkssh 0.2.0:
+
+- **alkvault 0.2** — the breaking req bump; the adapter seam's
+  `Zeroizing` wrap dropped (the known-gap ADR-005 decision 3 recorded
+  is closed upstream); ADR-005 §3 + OQ-07 amended per the entry's own
+  predicted one-line doc touch.
+- **alktunnels 0.5.0 + the W2 gate adoption** — the forwarded serving
+  surface registers
+  `register_tunnel_forwarded_openable_with_establisher` with a
+  `ForwardedGate` capturing the `ListenRouter`; stale-token arrivals
+  fail typed at the call plane before any channel is born; the
+  handler-side re-lookup stays as the residual-race +
+  cap-admission teardown-at-birth fallback. mapping.md's
+  `forwarded-tcpip` row updated; gate rows added (miss typed /
+  pass unchanged / residual-miss unit pin).
+- **alktty 0.8.2** — patch-level; pin text refreshed; OQ-10's
+  upstream PTY constraint retired (mapping.md rule 5 amended); the
+  real-tool PTY signal-fidelity e2e row deferred (booked follow-up).
+- Version 0.1.0 → 0.2.0 (dep-req changes are semver-significant for
+  consumers); CHANGELOG entry.
+
+## Notes
+
+- The e2e `real_git_push_creates_the_ref_through_the_door` row
+  flaked once under full-matrix load (prepared-assert raced the
+  accept_task abort; 6+ isolated passes on both parent and adoption
+  tree; no shared path with the gate adoption). Not a regression;
+  the row's abort-vs-record race is a standing e2e flake to watch.
+
+## Summary
+
+All three adoptions landed in one wave; the version is 0.2.0; the
+decline-matrix matrix runner, clippy ×2, fmt, doc, and the fuzz
+corpus gate are green.