fix: handle duplicate repository keys in Dictionary and NSMenu

[ggfevans]

Summary

• Replace Dictionary(uniqueKeysWithValues:) with Dictionary(_:uniquingKeysWith:) to prevent crashes when duplicate fullName keys occur
• Apply fix to all three locations in AppState+Refresh.swift that use this pattern
• New: Deduplicate repos by id in menu builder to prevent NSMenu crashes when cached items are added twice

Problem

The app crashes in two ways when duplicate repositories appear in the data:

1. Dictionary crash: EXC_BREAKPOINT (SIGTRAP) in _assertionFailure from _NativeDictionary.merge when mergeHydrated encounters repositories with duplicate fullName values
2. Menu crash: NSMenu assertion failure "Item to be inserted into menu already is in another menu" when the same cached NSMenuItem is added to the menu twice

Root Cause

Duplicate repository keys can occur when:

1. Pinned repositories have case variations
2. Same repo is returned via different code paths during hydration
3. Repository list contains duplicates before filtering

Solution

Dictionary fix

Use Dictionary(_:uniquingKeysWith:) which gracefully handles duplicates by keeping the first occurrence:

// Before (crashes on duplicates):
let lookup = Dictionary(uniqueKeysWithValues: detailed.map { ($0.fullName, $0) })

// After (handles duplicates):
let lookup = Dictionary(detailed.map { ($0.fullName, $0) }, uniquingKeysWith: { first, _ in first })

Menu fix

Deduplicate repos by id before iterating to build menu items:

// Deduplicate repos by id to prevent adding the same cached menu item twice
var usedRepoKeys: Set<String> = []
let uniqueRepos = repos.filter { repo in
    if usedRepoKeys.contains(repo.id) { return false }
    usedRepoKeys.insert(repo.id)
    return true
}

Test plan

• Build succeeds (swift build)
• App launches without crash with pinned repositories configured
• Existing tests pass (one unrelated network timeout in LoopbackServerTests)
• Menu opens without assertion errors

Fixes #31

🤖 Generated with Claude Code

[ggfevans]

heads up @steipete - low hanging fruit