feat(voyage): document --profile flag in all 6 commands — SC #4 + arv-policy

Step 7 av v4.1-execute (Wave 3, Session 4).

Legg ny "## Profile (v4.1)"-seksjon i hver kommando-fil rett før "## Hard rules":
- trekbrief.md: --profile + VOYAGE_PROFILE + premium default
- trekresearch.md: + economy/balanced auto-disable external_research_enabled
- trekplan.md: + plan.md frontmatter recording for inheritance
- trekexecute.md: + 4-step resolution (flag > env > inheritance > default)
- trekreview.md: + opus-default for review-deepening
- trekcontinue.md: spesiell — INHERITANCE er default (ikke premium), --profile
  overstyr emitter stderr-advarsel

Tester (13 nye, baseline 432 → 445):
- 6 commands × 2 (--profile + VOYAGE_PROFILE)
- trekcontinue.md "inheritance"-keyword

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

plugins/voyage/commands/trekreview.md

@@ -309,6 +309,28 @@ Per **Handover 6**, BLOCKER and MAJOR findings are consumed by
 review's frontmatter `findings:` list and the trailing JSON block are
 the contract for that handover (see `docs/HANDOVER-CONTRACTS.md`).
 
+## Profile (v4.1)
+
+Accepts `--profile <name>` where `<name>` is `economy`, `balanced`, `premium`,
+or a custom profile under `voyage-profiles/`. Default: `premium`.
+
+Resolution order (per `lib/profiles/resolver.mjs`):
+1. `--profile` flag (source: `flag`)
+2. `VOYAGE_PROFILE` env-var (source: `env`)
+3. `premium` default (source: `default`)
+
+The selected profile drives `phase_models.review` — `economy` uses sonnet
+for the brief-conformance + code-correctness reviewers; `balanced` and
+`premium` use opus (review benefits from deeper reasoning).
+
+Examples:
+```
+/trekreview --profile balanced --project .claude/projects/2026-05-09-add-auth
+VOYAGE_PROFILE=premium /trekreview --project ...
+```
+
+Stats records emit `profile` and `profile_source`.
+
 ## Hard rules
 
 - **Brief is the contract.** Every finding in the review traces to a