feat(analyze): hidden-space insights in overview

[sebastianbreguel]

Summary

Adds hidden-space insight entries to the mo analyze overview screen that surface disk usage in commonly overlooked locations. These appear alongside the standard directory entries (Home, App Library, Applications, System Library).

Many of these correspond to things mo clean already handles — this PR lets users see how much space each category uses before deciding to clean.

Discussed in #659 as features that fit naturally inside mo analyze.

New insight entries

Universal (everyone has these)

Entry	Path	Icon	Cleanable with mo clean?
Old Downloads (90d+)	~/Downloads (files >90 days)	📥	Manual — user decides what to keep
iOS Backups	~/Library/.../MobileSync/Backup	📱	Manual — manage in Finder/iTunes
System Caches	~/Library/Caches	💾	Yes — mo clean clears user caches
System Logs	~/Library/Logs	📋	Yes — mo clean clears old logs
Homebrew Cache	~/Library/Caches/Homebrew	💾	Yes — brew cleanup / mo clean

Developer-specific (only shown if installed)

Entry	Path	Icon	Cleanable with mo clean?
Xcode DerivedData	~/Library/Developer/Xcode/DerivedData	🔨	Yes — safe to delete, rebuilds on next build
Xcode Simulators	~/Library/Developer/CoreSimulator/Devices	📲	xcrun simctl delete unavailable
Xcode Archives	~/Library/Developer/Xcode/Archives	🔨	Manual — old build archives
Docker Data	~/Library/Containers/com.docker.docker/Data	🐳	docker system prune
Spotify Cache	~/Library/.../Spotify/PersistentCache	💾	Yes — mo clean handles app caches
JetBrains Cache	~/Library/Caches/JetBrains	💾	Yes — safe to delete
pip Cache	~/Library/Caches/pip	💾	pip cache purge
Gradle Cache	~/.gradle/caches	💾	Manual — gradle cleanBuildCache
CocoaPods Cache	~/Library/Caches/CocoaPods	💾	pod cache clean --all

Behavior

• Entries only appear if their path exists on the machine
• All entries open normally in analyze's directory view on Enter
• Scanned concurrently alongside standard overview entries
• 🧹 icon shown next to cleanable entries

Visual preview

  Analyze Disk
  Select a location to explore:

 ▶  1. ████████████████  45.2%  |  📁 Home                    210.5 GB
    2. ██████████░░░░░░  28.1%  |  📁 App Library             131.0 GB
    3. ████░░░░░░░░░░░░  10.3%  |  📁 Applications             48.0 GB
    4. ██░░░░░░░░░░░░░░   4.8%  |  📁 System Library           22.4 GB
    5. ██░░░░░░░░░░░░░░   3.2%  |  📲 Xcode Simulators         11.2 GB
    6. █░░░░░░░░░░░░░░░   2.4%  |  🔨 Xcode DerivedData         9.8 GB  🧹
    7. █░░░░░░░░░░░░░░░   2.1%  |  🐳 Docker Data               8.4 GB
    8. █░░░░░░░░░░░░░░░   1.8%  |  📥 Old Downloads (90d+)      7.0 GB
    9. █░░░░░░░░░░░░░░░   1.1%  |  💾 System Caches             4.2 GB  🧹
   10. ░░░░░░░░░░░░░░░░   0.4%  |  📱 iOS Backups               1.8 GB
   11. ░░░░░░░░░░░░░░░░   0.2%  |  💾 Homebrew Cache             0.9 GB  🧹
   12. ░░░░░░░░░░░░░░░░   0.1%  |  📋 System Logs               0.5 GB  🧹

Test plan

• go build ./cmd/analyze/ — compiles cleanly
• go vet ./cmd/analyze/ — no issues
• go test ./cmd/analyze/ — all tests pass
• New tests: TestCreateInsightEntries, TestInsightIcon, TestMeasureOldDownloads, TestMeasureInsightSizeFallsBackToOverview
• Entries only appear when their path exists

[tw93]

@sebastianbreguel Thanks for this, the hidden-space insight idea is solid and fits naturally into the overview.

Merged with two small follow-up fixes in 81c36e4:

• Removed System Caches from the insight list. Since Homebrew Cache, JetBrains Cache, pip Cache, and CocoaPods Cache are all subdirectories of ~/Library/Caches, listing the parent alongside them was double-counting the same bytes in the visual percentages.
• Hide zero-size entries after scanning. On machines that have never used Xcode Archives, Xcode DerivedData, or have no old downloads, those rows showed 0 B and added noise without providing actionable information. They are now filtered from the view once scanning completes.

The result is a cleaner list that only surfaces entries worth acting on.