docs(repo): README omits unic-spec-review and describes a retired unic-archon-dlc box set

[orioltf]

Parent: #297 · Found by the comprehensive review of #298 (L15) plus one adjacent defect

Problem

Two stale facts in README.md, both pre-existing and unrelated to #297's scope. They were deliberately
kept out of that PR rather than smuggled in alongside its two justified README edits.

1. unic-spec-review is missing from the plugin table (README.md:9-13) and from the install
   command list (:26-30). The plugin ships and has its own directory, marketplace entry and label.
2. unic-archon-dlc's description is the retired seven-workflow generation —
   "explore → plan → build → qa → cleanup → triage". The current box set, per that plugin's own
   README.md, is /specs → /tickets → /build → /pr-review → /qa with /triage as an on-ramp. This is
   the same stale generation docs/agents/workflow.md was deleted for in chore: de-dogfood unic-archon-dlc and upgrade Matt's skills to upstream main #298.

Acceptance criteria

• The plugin table lists every plugin under apps/claude-code/, checked against the directory
  listing rather than by eye
• The install list matches the table, one line per plugin
• unic-archon-dlc's description states the shipped main line and does not name a retired workflow
• No other row's description contradicts its plugin's own README.md

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🤖 Filed with Claude Code.