feat(init): support CLERK_SKILL_SOURCE env override

[wyattjoh]

Summary

Adds a CLERK_SKILL_SOURCE env var as an escape hatch for skill authors iterating on the clerk skill without rebuilding the CLI. When set, clerk init passes the value straight to <runner> skills add <value> in place of the bundled source (#126).

Any value the skills CLI accepts works:

# Absolute path to a working-tree skill dir (default symlink install,
# edits to the source are reflected in the installed skill immediately).
CLERK_SKILL_SOURCE="$PWD/skills/clerk" clerk init

# A fork or PR branch on GitHub.
CLERK_SKILL_SOURCE="https://github.com/me/cli/tree/wip/skills/clerk" clerk init

# Shorthand for the default repo (installs from main branch).
CLERK_SKILL_SOURCE="clerk/cli" clerk init

The override path skips the staged temp dir and the --copy flag introduced in #126, so a local working-tree path installs via the default symlink mode and edits to the source are picked up by already-installed projects without re-running clerk init. init logs the value being used so there's no surprise about what got installed.

The override has no effect on the upstream skills.

Stacked on #126.

Test plan

• bun run test passes (unit tests cover env-var precedence: unset, empty/whitespace, trimmed / remote / local variants)
• Manual: CLERK_SKILL_SOURCE="$PWD/skills/clerk" bun run dev -- init in a sandbox, confirm the installer logs the override and .claude/skills/clerk/ is a symlink into the working tree
• Manual: edit skills/clerk/SKILL.md in the working tree, re-open the installed skill, confirm the edit is visible without re-running init
• Manual: CLERK_SKILL_SOURCE="clerk/cli" bun run dev -- init installs from the remote shorthand and the upstream framework skills still install normally

[wyattjoh]

Stack: feat/clerk-cli-skill-local-debug

• feat(lib): add NonEmptyArray helper, tighten preferredRunner #125
• feat: Clerk CLI Skill #126
  • feat(init): support CLERK_SKILL_SOURCE env override #127 👈 this PR

Part of a stacked PR chain. Do not merge manually.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a7a6cbd5-974d-469d-8e35-f262cc931127

📥 Commits

Reviewing files that changed from the base of the PR and between 1aa3777 and 0e9207d.

📒 Files selected for processing (6)

• .changeset/clerk-skill-local-debug.md
• packages/cli-core/src/commands/init/README.md
• packages/cli-core/src/commands/init/skills.ts
• packages/cli-core/src/commands/skill/README.md
• packages/cli-core/src/commands/skill/install.test.ts
• packages/cli-core/src/commands/skill/install.ts

✅ Files skipped from review due to trivial changes (2)

• .changeset/clerk-skill-local-debug.md
• packages/cli-core/src/commands/skill/README.md

🚧 Files skipped from review as they are similar to previous changes (2)

• packages/cli-core/src/commands/init/skills.ts
• packages/cli-core/src/commands/skill/install.test.ts

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📝 Walkthrough

Walkthrough

Adds a CLERK_SKILL_SOURCE environment variable that, when set, causes the CLI to pass that value directly to the underlying skills add <source> invocation instead of staging and copying the bundled clerk skill. Implementation includes a new exported resolveClerkSkillOverride helper, changes to installClerkSkillCore to honor the override (and log it), unit tests covering both override and default staging behavior, and README entries plus a changeset documenting the feature.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'feat(init): support CLERK_SKILL_SOURCE env override' clearly and concisely describes the main change: adding support for a CLERK_SKILL_SOURCE environment variable to the init command.
Description check	✅ Passed	The description comprehensively explains the purpose of CLERK_SKILL_SOURCE, provides concrete usage examples, documents the technical behavior, and includes a test plan—all directly related to the changeset.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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