feat: Global config merge with override support

[Gerkinfeltser]

Summary

• Load both user global (~/.config/opencode/command-hooks.jsonc) and project (.opencode/command-hooks.jsonc) configs
• Concatenate hooks by default — both run
• Add overrideGlobal flag to suppress global hooks for same event
• Add ignoreGlobalConfig flag to skip global config entirely

Note: Windows users will also need #1 merged for hooks to work at all.

Behavior

Scenario	Result
Different hook IDs	Both run (concatenation)
Same hook ID	Project replaces global
overrideGlobal: true on hook	Suppresses all global hooks for same event/phase+tool
ignoreGlobalConfig: true in project config	Skips ~/.config/opencode/ entirely
Tool hook with tool: "*" + overrideGlobal	Suppresses ALL global hooks for that phase

Example

// ~/.config/opencode/command-hooks.jsonc (global)
{
  "session": [
    { "id": "global-idle", "when": { "event": "session.idle" }, "run": "echo global" }
  ]
}

// .opencode/command-hooks.jsonc (project)
{
  "session": [
    { "id": "project-idle", "when": { "event": "session.idle" }, "run": "echo project" }
  ]
}
// Result: both hooks fire

To override all global hooks for an event:

{
  "session": [
    { 
      "id": "project-idle", 
      "when": { "event": "session.idle" }, 
      "run": "echo only this runs",
      "overrideGlobal": true
    }
  ]
}

Changes

• src/types/hooks.ts — added overrideGlobal and ignoreGlobalConfig types
• src/schemas.ts — added fields to Zod schemas
• src/config/merge.ts — added overrideGlobal filtering logic
• src/config/global.ts — loads both configs and merges them
• tests/config.global.test.ts — 14 tests for merge behavior
• README.md — updated docs

Testing

bun test tests/config.global.test.ts  # 14 pass
bun test                               # 99 pass, 6 pre-existing failures