fix: Show "edit" instead of "create" in permission prompt for existing files

[charlesvien]

Problem

Write tool permission prompts always say "Create new file" even when overwriting an existing file, because the old file content was never resolved during the permission request flow.

Closes #1529

Changes

1. Add disk-read fallback in Write tool case when file isn't in the content cache
2. Pass fileContentCache and cwd to toolInfoFromToolUse in permission flow so cached content and relative paths are available

How did you test this?

Manually

[charlesvien]

• fix: Fix stale context usage after compaction + usage calculation #1548
• fix: Show both local and remote repo name when they differ #1547
• fix: Queue messages during conversation compaction #1546
• fix: Prevent permission request from stealing focus across cells #1545
• feat: Add double-click to rename task title in session header #1544
• fix: Reduce unnecessary IPC calls causing UI unresponsiveness #1542
• fix: Move folder cleanup and orphaned worktree pruning to main process #1541
• fix: Show "edit" instead of "create" in permission prompt for existing files #1538 👈 (View in Graphite)
• fix: Remove double scrollbar from repo selector #1537
• main

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[charlesvien]

Merge activity

• Apr 8, 11:25 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Apr 8, 11:26 PM UTC: Graphite rebased this pull request as part of a merge.
• Apr 8, 11:33 PM UTC: @charlesvien merged this pull request with Graphite.