fix(docs): no doc claims an opus orchestrator any more; research spawns use the resolved model

D-07 had been closed on CLAUDE.md alone. The same false claim lived on elsewhere:
- README.md's "Switch the planning model" said four commands default to opus.
- The same README section offered a sed recipe for `model: opus` frontmatter lines, which
  0 of 7 command files have.
- commands/trekresearch.md said "the orchestrator runs on Opus".
Since v5.9.0 no command pins model:, so the orchestrator follows the session model.

- README: the section now says how it actually works. You pick the orchestrator's model with
  the session model (`claude --model sonnet` or `/model`). Sub-agent models are resolved at
  the spawn sites: brief phase_signals, then profile phase_models, then the agents/*.md pins
  as fallback. `--profile economy` still moves the sub-agents to Sonnet.
- trekresearch Launch rules: "Use model: "opus" for all sub-agents" contradicted the same
  file's own three-layer resolution, which v5.9.0 wired into the spawn sites and the file
  documents in Phase 1 and Hard rules -> Cost. The rule now injects
  `phase_signal_result.model` with agent frontmatter as the fallback, and says the
  orchestrator follows the session model. Nothing changes under the default premium
  profile: it still resolves to opus. The engine=swarm note now names the resolved-model
  injection as the anchor, instead of the removed literal.
- Two doc-consistency pins were written first and failed before this change:
  - no opus-orchestrator claim in README/CLAUDE.md/trekresearch, and no `^model: opus$`
    recipe;
  - the Launch rules name `phase_signal_result.model` and carry no blanket opus rule.
- Not touched: the follow-up agent in the default-off STORM phase still says model: "opus".
  That is part of an experiment whose fate is an operator decision.

End-state gate D-07: open -> closed. Defects 3 -> 2 of 7 (D-03, D-04 remain, by design);
registry integrity intact. Suite 1081 (1079/0/2), run on a clean export of the index.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -885,22 +885,15 @@ synthesis.
 
 ### Switch the planning model
 
-The default for `/trekbrief`, `/trekresearch`,
-`/trekplan`, and `/trekexecute` is `opus` (deep
-reasoning). To run on Sonnet for cost or latency, search-and-replace
-the frontmatter in these four command files:
+The command orchestrators pin no model: `/trekbrief`, `/trekresearch`,
+`/trekplan`, and `/trekexecute` run on whatever model the session runs on.
+To run them on Sonnet for cost or latency, start the session on Sonnet
+(`claude --model sonnet`) or switch with `/model` inside the session.
 
-```bash
-sed -i.bak 's/^model: opus$/model: sonnet/' \
-  commands/trekbrief.md \
-  commands/trekresearch.md \
-  commands/trekplan.md \
-  commands/trekexecute.md
-```
-
-This flips only the four command orchestrators. The exploration and review
-sub-agents in `agents/*.md` are separately `opus`-pinned — flip those too, or
-just run `--profile economy`, to put the whole pipeline on Sonnet.
+The exploration and review sub-agents are chosen separately, at the spawn
+sites: brief `phase_signals` first, then the profile's `phase_models`, with the
+`model: opus` pins in `agents/*.md` as the fallback. Run `--profile economy`
+to put the sub-agents on Sonnet as well.
 
 ### Disable external research