Group shell actions and bundle default skills

[davidtaylor6130]

What changed

• group all Windows Explorer actions under a native Universal Agent Manager submenu with the app icon
• support nested action groups, persisted and editable in Settings
• discover .uam files recursively and preserve their folder structure
• seed executable-adjacent bundled skills into writable user storage without overwriting existing or customized entries
• add evidence-first Coding and SVN starter workflows
• move the five existing GitHub workflows into the bundled folder without changing their contents
• add GPT-5.6 ultra reasoning support across UI, persistence, validation, and Codex requests

Why

The previous Windows integration placed every action directly in the main context menu, the skill library only handled a flat directory, and packaged defaults were not safely editable in protected installation locations.

Validation

• UI: 376/376 Vitest tests passed
• native: all 3 CTest targets passed
• macOS app rebuilt and strict code-sign verification passed
• packaged skill tree exactly matches source (18 .uam files)
• adversarial forward tests passed for Log Analysis, Security Audit, and SVN tagging
• pre-push security audit found no current secret or private-key candidates
• GitHub workflow contents verified byte-for-byte unchanged
• PR CI: macOS passed
• PR CI: Windows passed, including isolated shell-menu migration/re-apply coverage and executable smoke launch