docs(brief): the surfaces register matches v0.12.0's commands

[REPPL]

The brief's surfaces register now matches v0.12.0's commands. An independent docs review of the release candidate held the cut on five sentences in .abcd/development/brief/04-surfaces/README.md that still described an earlier command tree; this change corrects them, and one code comment that carried the same stale claim.

The five changes, each checked against the code it cites:

1. The drain row in the chapter table describes drain as it ships: work the open ledger unattended, preview with --dry-run, then run it one lane at a time, routing every hand-back by its kind (internal/surface/cli/drain.go runs one move of the run without --dry-run).
2. The bare-invocation paragraph says bare abcd drain is the run itself, one move per invocation, so it is not a render; what a drain would do renders through its dry run.
3. The people/release row lists reflect beside launch (internal/surface/cli/helpgroups.go).
4. The agents-block row lists intent consistency ingest, intent prepass and lab (helpgroups.go; commands/lab.md declares block: agents).
5. The person-verb cap reads fifteen, the ceiling consolidate_test.go holds.

The bare-render exception reason for drain in internal/surface/cli/barerender.go now says what the bare verb does. That text is read only by the bare-render test, so no behaviour changes.

Gates: go test ./internal/surface/cli/..., record-lint, docs-lint and abcd docs fidelity --report (layer 1: 164 of 164) pass; make preflight passes and minted the push receipt.

Assisted-by: Claude:claude-opus-5-5