FEAT-133: Fix approval dialog labels and add none tier

[shafty023]

• Fix misleading approval reason: show operation risk tier, not user threshold
• Add color-coded risk badge (low/medium/high) to approval card header
• Replace 'auto' tier with 'none' (prompt for all operations)
• Add 'none' to riskTierOrder (returns 0, blocks all auto-approvals)
• Migrate persisted 'auto' values to 'high' in SettingsStore constructor
• Clarify dropdown labels to describe when user will be prompted
• Preserve Exclude<RiskTier, 'none'> for operation risk types (type safety)

Testing:

• just desktop-typecheck passes
• just desktop-test passes (288/288)
• just desktop-lint passes

Risks:

• Users with persisted 'auto' tier get migrated to 'high' (same behavior)
• The 'none' tier is new; users must explicitly select it

[closedloop-ai-stage]

Code Review Summary

Status: Approved

Reviewers: Bug Hunter A, Bug Hunter B, Unified Auditor, Premise Reviewer, electron-specialist

Findings

Severity	Count
Blocking	0
High	0
Medium	1

MEDIUM Issues (consider)

1. [P3] [apps/desktop/test/settings-migration.test.ts:143] Weak assert.notEqual assertions allow false-positive passes

The persisted-JSON verification uses negative assertions that pass when keys are absent.
Use assert.equal to confirm the migrated values are set to the expected string.

Validation Stats

• Agent failures: 0 partitions skipped
• Cross-file grouped: 0 findings consolidated

Recommendation: Approve - no blocking or high-severity issues. Consider strengthening test assertions.