ux: default 'charter' view should show risk signal for installed repos, not adoption pitch

[stackbilt-admin]

Problem

Running charter (no subcommand) on a repo that already has it installed returns:

Charter Quickstart
Turns governance from abstract policy into merge-time guardrails.

Repo snapshot:
  - Git repo: yes
  - Governance baseline (.charter): installed
  - Recent commits scanned: 20
  - Governance-linked commit coverage: 5%
  - High-risk commits without governance links: 0

Why teams use Charter:
  - Catch risky, unreviewed changes before merge
  ...

Next action: Run: charter audit --format text for a shareable governance posture report

The "Why teams use Charter" block is shown every time even on repos where charter is already adopted. For daily developer use, this is noise — they don't need to be sold on a tool they've already installed.

Proposed UX

Split the default view into two modes:

First-time / not-installed (no .charter/ dir): show the current adoption pitch + quickstart

Installed (.charter/ exists): show a compact daily posture view:

charter — governance snapshot (2026-05-23)
  Coverage:  5%  (↓ from 12% last week)   [warn]
  Patterns:  0 active                       [warn]
  Drift:     no patterns to scan
  Last audit: 2 days ago — score 0/100      [fail]

Run 'charter audit' for full report · 'charter doctor' to fix warnings

This makes charter a useful daily status command rather than a one-time onboarding tool. The adoption content can live in charter why (which already exists).

Notes

• Trend tracking (↑/↓) could be stored in .charter/history.json or derived from git history
• The compact view should exit non-zero if any [fail] is present when --ci flag is used

[stackbilt-admin]

Fixed in PR #176.