Review permission changes during repeat installs

[LadyBluenotes]

Problem

Once interactive permission setup exists, later intent install runs need to distinguish current decisions from newly discovered and no-longer-discovered candidates. Repeating the full first-run flow would create noise, while applying policy edits without review would make configuration changes hard to audit.

User outcome

A repeat install shows meaningful permission changes, preserves unchanged decisions, and requires confirmation before it edits policy.

In scope

• Compare the effective intent.skills policy with the current discovered package and skill candidates.
• Show newly discovered packages and skills separately from unchanged candidates.
• State whether each new candidate is controlled by an explicit package entry, the per-skill rules from Support reviewable per-skill permissions #219, a wildcard, allow-all mode, absent migration mode, empty deny-all mode, or intent.exclude.
• Show configured packages or skills that are no longer discovered without claiming they are uninstalled.
• Preserve unchanged permission decisions without asking the human to select them again.
• Preserve the documented meaning of package-level entries, wildcards, allow-all mode, absent migration mode, empty deny-all mode, inheritance, and exclusions.
• Report a candidate already permitted by a broader rule without presenting it as a required new permission decision; allow the human to narrow the broader rule as an explicit policy change.
• Require explicit confirmation before adding, removing, or changing policy entries.
• Do not remove configured-but-undiscovered entries automatically.
• Explain whether the run changes permissions, guidance, both, or neither.

Out of scope

• Byte-level content drift.
• Content locks, hashes, or lockfile state.
• Delivery, placement, or synchronization state.
• Git sources.

Acceptance criteria

• Repeat install reports newly discovered packages and skills separately from unchanged candidates.
• Each new candidate shows whether the current policy permits or blocks it and which policy form controls that result.
• The controlling result accounts for intent.exclude after intent.skills permission is evaluated.
• Repeat install reports configured packages or skills that are no longer discovered using "not discovered" language.
• Unchanged permission decisions are retained without reasking for them.
• Existing package-level entries, wildcards, allow-all mode, absent migration mode, and empty deny-all mode keep their documented meaning.
• A candidate already covered by a broader permission is not presented as requiring a redundant permission entry.
• The command never adds a new explicit permission entry without confirmation.
• The command never removes a configured-but-undiscovered entry without confirmation.
• Permission additions, removals, and changes are previewed before confirmation.
• Canceling a review leaves the configured permissions unchanged.
• A failed validation or write does not leave a partial permission update.
• The result distinguishes permission changes from guidance changes.
• The review does not claim to detect content, byte, lockfile, or delivery drift.

Dependencies

• Support reviewable per-skill permissions #219
• Add interactive skill permission setup to intent install #220

Prior exploration

#204 explored repeat install together with accepted-content and delivery deltas. This issue is limited to permission configuration and discovery changes.