feat(activation): add provider-agnostic Chalk activation contract

[breadoncee]

Summary

• Define a neutral Chalk activation contract for project-level skill routing without introducing provider-specific runtime behavior
• Add an example .chalk/activation/skills.yaml manifest and document how project activation rules relate to skill-level activation hints
• Extend validation and scaffolding to support activation metadata across the shipped Chalk skills

Changes

Activation contract

• docs/activation-model.md — Defines the neutral project manifest shape, supported matchers/actions, conflict resolution, and rollout guidance
• docs/examples/activation-skills.yaml — Adds a concrete example manifest showing prompt-, path-, and capability-driven activation rules
• docs/skill-contract.md — Introduces metadata-version: "2" and optional activation hint fields: capabilities, activation-intents, activation-events, activation-artifacts, and risk-level
• Repo docs — Updates README.md, docs/open-source-scope.md, docs/versioning.md, CONTRIBUTING.md, docs/review-checklist.md, and CHANGELOG.md to describe the new contract while keeping this repository provider-agnostic

Tooling

• scripts/validate-skills.sh — Validates activation metadata for metadata-version: "2" while remaining backward-compatible with legacy metadata-version: "1" skills
• scripts/init-skill.sh — Scaffolds the new activation metadata fields for newly created skills and enforces valid schema/risk-level usage

Core skills

• Adds activation hints to the shipped core skills so a future Chalk Browser router can reason about them without parsing prose only
• Keeps the hints broad and reusable instead of baking in project-specific routing logic
• Keeps runtime routing, adapters, and provider-specific execution out of this repo; this PR defines the portable contract only

Why this matters

Chalk Browser can now target one stable activation schema instead of inferring routing purely from descriptions or binding directly to a provider-specific hook format. Projects get a portable .chalk/activation/skills.yaml contract, while Browser remains free to implement the runtime layer separately.

Test plan

• bash scripts/validate-skills.sh passes for all 13 skills

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request establishes a foundational, provider-agnostic mechanism for skill activation within the Chalk ecosystem. By introducing a new activation model and extending skill metadata, it enables more flexible and intelligent routing of skills based on user intent, events, and project context. This change enhances the discoverability and usability of skills across different runtimes, laying the groundwork for advanced automation and integration without vendor lock-in.

Highlights

• Provider-Agnostic Activation Contract: Introduced a new, neutral contract for skill activation, allowing runtimes to decide when to load skills without being tied to specific providers. This includes a new docs/activation-model.md and an example manifest docs/examples/activation-skills.yaml.
• Extended Skill Frontmatter: The skill frontmatter schema (metadata-version: "2") was extended to include new, optional activation metadata fields such as capabilities, activation-intents, activation-events, activation-artifacts, and risk-level.
• Updated Tooling and Documentation: Scaffolding (scripts/init-skill.sh) and validation tooling (scripts/validate-skills.sh) were updated to support the new activation metadata. Contributing guidelines, README, and review checklists were also updated to reflect these changes.
• Activation Hints for Shipped Skills: All existing Chalk skills were updated to metadata-version: "2" and now include activation hints, providing a foundation for future routing in tools like Chalk Browser.

Changelog

• CHANGELOG.md
  • Added an activation model specification document.
  • Added an example project activation manifest.
  • Extended the frontmatter contract with provider-agnostic activation metadata (metadata-version: "2").
  • Updated scaffolding and validation tooling for activation metadata.

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[gemini-code-assist]

Code Review

This pull request introduces a provider-agnostic activation contract for Chalk skills, which is a significant enhancement. The changes include a new activation model specification, updates to the skill contract to version 2, and extensions to the scaffolding and validation scripts to support the new activation metadata. The implementation is well-structured, and the documentation is comprehensive. I have a few suggestions to improve the robustness of the scripting and clarity of the new activation model documentation.