fix: reclassify geminicli as native skill with global support

[mrfelton]

Summary

Fixes #974 — Reclassifies the geminicli target from a "simulated" skill to a native ToolSkill, reflecting Gemini CLI's native skills support.

Problem

GeminiCliSkill currently extends SimulatedSkill and is marked with supportsSimulated: true, which means:

• Without simulateSkills: true, geminicli is excluded from skill generation
• .gemini/skills/ never gets populated by default
• The source comment "Since Gemini CLI doesn't have native skill support" is outdated

Changes

src/features/skills/geminicli-skill.ts

• Complete rewrite from SimulatedSkill → ToolSkill (native base class)
• New GeminiCliSkillFrontmatterSchema (zod/mini looseObject with name + description)
• Proper constructor with global mode support
• Full native lifecycle: validate(), getFrontmatter(), getBody(), toRulesyncSkill(), fromRulesyncSkill(), fromDir(), forDeletion(), isTargetedByRulesyncSkill(), getSettablePaths()
• Both project (.gemini/skills/) and global (~/.gemini/skills/) modes supported

src/features/skills/skills-processor.ts

• Updated geminicli factory metadata: supportsSimulated: false, supportsGlobal: true

src/features/skills/geminicli-skill.test.ts

• Comprehensive test rewrite covering: constructor, validation, schema (including loose object behavior), fromDir, getSettablePaths (project + global), conversion (toRulesyncSkill, fromRulesyncSkill, fromRulesyncSkill with global), isTargetedByRulesyncSkill, forDeletion

src/features/skills/skills-processor.test.ts

• Updated getToolTargets() assertions: geminicli now appears in default/native target lists
• Removed geminicli from simulated target list assertions
• Added geminicli to global target list assertions

Evidence

Gemini CLI officially supports the Agent Skills open standard:

• Docs: https://geminicli.com/docs/cli/skills/
• Skills discovered from .gemini/skills/ (workspace) and ~/.gemini/skills/ (user)
• Full native lifecycle: discovery → activation → consent → injection → execution
• Based on the Agent Skills open standard

Testing

All existing tests pass with the changes. Test suite: 139 files, 3696 tests passing.