fix: Show clear output when enable partially succeeds

Problem

When mi6 enable claude gemini codex runs and one framework fails, the user does not clearly see which ones succeeded vs failed.

Current behavior:

• Frameworks are enabled sequentially
• If framework N fails, error is shown but it is unclear that 1..N-1 succeeded
• User may retry and accidentally skip already-enabled frameworks

Example Scenario

$ mi6 enable claude gemini codex
error: failed to enable codex: config.toml has invalid TOML syntax

User does not know Claude and Gemini were successfully enabled.

Proposed Output

$ mi6 enable claude gemini codex

Enabled:
  claude  -> ~/.claude/settings.json
  gemini  -> ~/.gemini/settings.json

Failed:
  codex   -> config.toml has invalid TOML (line 12)

1 framework failed. Fix the errors and retry with: mi6 enable codex

Scope

• Collect results from each framework enable
• Display summary at end instead of failing fast
• Continue enabling remaining frameworks even if one fails