docs(wiki): context7-setup concept → CLI-first canonical

Concept page (2026-04-28) still documented the plugin context7@claude-plugins-official as single source — stale vs setup-context7 v2.0.0 CLI-first migration (2026-08-12). Rewrote: CLI + key in ~/.config/projects-secrets/ctx7.env as canonical, plugin era demoted to rollback-only, whoami!=key-check gotcha recorded. Index entry + log updated. Surface: review finding on session-ritual-context7-pins-review (already closed VERDICT PASS).

.wiki/index.md

@@ -24,7 +24,7 @@ Catalog of all wiki pages. One line per page, organized by type. Updated on ever
 - [build-notes.md](concepts/build-notes.md) — why `build.ps1` exists alongside `build.sh`; PS 5.1 backslash-in-zip gotcha; how to extract a `.skill`
 - [install-cross-platform.md](concepts/install-cross-platform.md) — paired-script parity contract for `install.{ps1,sh}` AND `build.{ps1,sh}`; rationale for the `--prune` / `-Prune` flag (combined-with-action, global-scan, default-off); install-side prunes target dirs, build-side prunes `dist/*.skill` files
 - [install-portability.md](concepts/install-portability.md) — `install.sh` / `build.sh` rewritten to drop `mapfile` (bash 4+) and `find -printf` (GNU only) so stock macOS (bash 3.2 + BSD find) works
-- [context7-setup.md](concepts/context7-setup.md) — switched context7 from manual MCP entries to the official plugin; API key in `.mcp.json` as `--api-key`; now also captured as `setup-context7` skill (one-time install/migrate flow with key discovery)
+- [context7-setup.md](concepts/context7-setup.md) — context7 CLI-first (2026-08-12): `ctx7` CLI + key in `~/.config/projects-secrets/ctx7.env`, plugin `context7@claude-plugins-official` + manual MCP entries removed; setup-context7 skill (one-time install/migrate, confirmation gates) + using-context7 policy; plugin era = rollback reference
 - [projects-meta-skills.md](concepts/projects-meta-skills.md) — `setup-projects-meta` + `using-projects-meta` skill pair for the local `projects-meta-mcp` stdio server (cross-project tasks + shared Gitea wiki); local-first rule + two-step mutation pattern
 - [project-discipline-design.md](concepts/project-discipline-design.md) — design for project-discipline (four cross-project rules: conventions-over-defaults, master-only, semver-bumping, ask-before-push)
 - [pulling-before-work-design.md](concepts/pulling-before-work-design.md) — design for the pulling-before-work skill (mode-3 + skip-on-dirty)