v7.54.0

Paired engine: engine-service-v0.1.129 (REQUIRED_ENGINE_VERSION (0, 1, 129)),
unchanged from 7.53.0. No engine cut: pin and cloud are both at v0.1.129 with
no service/src/main drift.

This release is what makes the plugin-side fixes below LIVE. Claude Code loads
the plugin from the tag marketplace.json pins, so every change under
conexus/ since 7.53.0 has been inert in every session until now. The fork
matcher is the one that matters most: until this tag, /branch fired no hook
at all, for anyone.

Plugin changes that become active with this release

• conexus/hooks/hooks.json: the SessionStart matcher gains fork, so
  /branch and --fork-session run the session-start hook (nexus-kdxyv).
• conexus/hooks/scripts/mailbox_drain.py: the dead _session_marker_names
  is deleted (nexus-kdxyv).
• Five skills (conexus/skills/research-synthesis, strategic-planning, architecture, debugging and deep-analysis) each stated a default
  model their own agent's frontmatter contradicts; all five now name the
  pinning file and what omitting model actually gets (nexus-3uxbc).

Fixed

• Retired CLI verbs no longer appear in --help (nexus-uks83). Six groups'
  worth: four in nx aspects, four in nx catalog, one in nx taxonomy, one
  in nx t3. Each still EXISTS and still refuses loudly with guidance naming
  what to do instead, because answering an old invocation with "No such
  command" drops that guidance; they are hidden, not deleted, following the
  link-* verbs in nx catalog that were already hidden the same way.

• The git hook stanza now passes --since-head (nexus-0l5so). That flag
  was built as "the per-commit fast path the removed git hooks needed"
  (b384357), and docs/cli-reference.md has described it that way ever
  since, but the stanza nx hooks install writes never carried it, so every
  commit paid the full-repo tax the flag exists to remove. It falls back
  loudly to a full index whenever the delta is unusable (no stored base, an
  unreachable one after a rewrite, a parse surprise), which is what makes it
  correct on post-merge and post-rewrite as well as post-commit.
  Existing installs keep the old stanza until nx hooks update; nx doctor
  reports the drift.

• A /clear or /resume handoff now moves the channel waiter with the
  session (nexus-kdxyv). The MCP server's T1 handoff swapped the session
  id but left the channel waiter and subscription set built for the old
  id running: the old mailbox's references kept flowing into the new
  conversation, no channel-status record was written for the new id, the
  old instance name's directory lease kept heartbeating, and teardown
  never cancelled the old waiter. The handoff now cancels the old waiter
  (recording alive: false under the old id), releases the old
  subscription set's directory/<name> row within about a second (the
  RDR-208 release, re-sending the same nonce with a one-second TTL, which
  tuple_unsubscribe now performs too) and starts a waiter under the new
  id.

• A resumed session no longer restores its old instance-name mailbox.
  nexus.mcp.subscriptions.load() restored the whole subscription list on
  a /resume, instance mailbox included, but the ListAgents name changes
  at every process start, so the restored name was stale by construction:
  its directory/<name> lease was re-armed for the life of the new
  process, and the session's own tuple_subscribe under its NEW name was
  then refused as a second instance mailbox. Board topics still restore.
  This is what RDR-211 already describes ("a /resume under a new name
  repeats it, and the old name's mail strands"); the old name's row now
  lapses at its TTL from the previous process's exit.

• /branch and --fork-session are handoff sources. Claude Code has
  reported them to SessionStart as source fork since 2.1.213; the
  plugin's matcher excluded it, so a fork fired no hook, the session
  marker kept naming the parent, and the parent's waiter pushed the
  parent's mail into the fork. fork joins the matcher and the wheel's
  _T1_HANDOFF_SOURCES: the marker moves to the fork, no cleared record
  is written (the parent's mailbox stays with the parent, RDR-208), and
  the waiter and lease follow the fork. The T1 scope moves with it, which
  JDR-001 lists only for /clear and /resume.