fix(kilo-subagent): align read defaults

[sirmacik]

Summary

Draft follow-up for #1634. This addresses the Kilo subagent default-mode cleanup from the maintainer-scrap issue.

Changes

• Give Kilo its own subagent frontmatter schema with mode defaulting to all.
• Route generated Kilo frontmatter through that schema so the default is centralized.
• Align fromFile and deletion placeholders with the same default.
• Strengthen the explicit kilo.mode: all test so it also proves other Kilo-specific fields survive.
• Document Kilo's default and the kilo.mode: subagent opt-out in file-format docs and synced skill docs.
• Update Kilo docs links from kilocode.ai to kilo.ai.

Fixes #1634.

Verification

• pnpm test src/features/subagents/kilo-subagent.test.ts
• pnpm test:e2e src/e2e/e2e-subagents.spec.ts
• pnpm cicheck

Review notes

Opened as draft to signal ownership of the maintainer-scrap follow-up while keeping review pressure low. Local regression-gate review and PAL review were run; the only follow-up identified is a broader future cleanup to separate per-target subagent schemas from the shared OpenCode-style base constructor.

[github-actions]

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[dyoshikawa]

@sirmacik Thank you!