captain: train land per slot under changelog_fragments (skill and skills.md)

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

docs/skills.md

@@ -45,7 +45,7 @@ Detailed guides for every gstack skill — philosophy, workflow, and examples.
 | [`/write-skill`](#write-skill) | **Skill Editor** | Write or improve an agent skill without bloat: edit ladder, size per level, skill-to-bin drift check, full diets with a before/after test. |
 | [`/test-audit`](#test-audit) | **Test Auditor** | Sweep existing tests for low-value, implementation-coupled or duplicate tests. Report-only unless you approve a batch. |
 | [`/landing-report`](#landing-report) | **Ship Queue Dashboard** | Read-only snapshot of the workspace-aware ship queue. Which version slots are claimed, which sibling workspaces have WIP. |
-| [`/captain`](#captain) | **Crew Controller** | Run many coding agents from one controller. Lanes build and send a READY block; the controller validates it, merges through trains (stamp on call, verify, merge with the expected head, verify again), keeps the digest, relays approvals in three fixed shapes and runs a daily flaky-fix pass. Also answers to `/crew`. |
+| [`/captain`](#captain) | **Crew Controller** | Run many coding agents from one controller. Lanes build and send a READY block; the controller validates it, merges through trains (stamp on call, verify, merge with the expected head, verify again; `train land` per slot under `changelog_fragments`), keeps the digest, relays approvals in three fixed shapes and runs a daily flaky-fix pass. Also answers to `/crew`. |
 | [`/benchmark-models`](#benchmark-models) | **Model Benchmark** | Side-by-side cross-model benchmark for skills (Claude vs GPT vs Gemini). Latency, tokens, cost, optional LLM-judged quality. |
 | [`/eval-plan`](#eval-plan) | **Eval Planner** | Preregister a paid eval (bars, arms, decoys, stop rules), dry-run it for $0 with the stub model, pilot three priced items, then approve the spend from the extrapolation table. |
 | | | |
@@ -1464,7 +1464,9 @@ receipt at the pin and the logged flaky cases); a green PR page or a cheap test
 never merge evidence. The controller batches READY pins into a **merge train**, reads one
 full gate on the train head (an in-run flaky rerun once; a case that failed twice is
 real), then merges slot by slot: slot call, lane stamps on call with a commit that holds
-only tool output, `verify --train`, `gh pr merge --match-head-commit`, verify again. A red
+only tool output, `verify --train`, `gh pr merge --match-head-commit`, verify again. Under
+`changelog_fragments` there is no slot call: `train land` publishes each slot's stamped
+prefix and merges it. A red
 train is bisected on its red cases and rebuilt at most once; a backstop gate on every
 base push freezes the queue when a tree no train covered lands. Approvals have three
 shapes (the per-thread record, the plan ask with before → after and a "do it" reply, the