feat(cli): scriptable output, shell completion, and CLI refactor

[Remeic]

Replaces #51 (closed when its branch was renamed feat/senior-polish → feat/scriptable-output).

Summary

Builds on the existing foundation (100% coverage + 100% mutation, multi-OS CI, release automation). Focus: scriptability, CLI craft, removing duplication — plus docs that surface the transactional design.

Changes

Refactor — refactor(cli)

• src/lib/errors.ts — shared formatError (was duplicated in profile-store.ts + profile-config-copy.ts)
• src/lib/ui.ts — central output/colors/icons on node:util styleText; NO_COLOR / non-TTY aware
• src/lib/run-action.ts — uniform CLI error handling (✗ message + exit 1); removes ~9 duplicated catch blocks and fixes list which previously had none

Features — feat(cli)

• ccm list --json / ccm status --json — machine-readable output; shared projection in profile-view.ts (emits null, not the — placeholder)
• ccm completion <bash|zsh|fish> — command list derived from the live registry, never drifts

Docs — docs

• ARCHITECTURE.md — state reconciliation, transactional stage→mutate→finalize + rollback, the testability DI seam, why error handling lives in runAction not index.ts
• CLAUDE.md, .editorconfig, README (--json + completion), CONTRIBUTING link

Quality gates

• ✅ Lint (Biome), Build (tsup)
• ✅ 365 tests (was 326)
• ✅ Coverage 100% (statements / branches / functions / lines)
• ✅ Mutation (Stryker) 100.00%, 0 survivors — every new file added to mutate[]; list.ts/status.ts newly mutated and brought to 100%
• ✅ Rebased on latest main (0.6.0 release, TypeScript 6.0.3) — gates re-verified

Verify

ccm list --json | jq '.[] | select(.loggedIn) | .name'
ccm completion zsh
NO_COLOR=1 ccm status   # no ANSI escapes