feat: vendor stokowski for Linear-driven agent orchestration

[bougyman]

Summary

• Vendors Sugar-Coffee/stokowski as a git submodule (vendor/stokowski) and checks in a shared workflow.yaml + .ai/prompts/*.md - safe to commit since tracker.api_key is omitted entirely, so Stokowski resolves it from the LINEAR_API_KEY env var at runtime rather than anything in the file.
• Adds mix stokowski (root repo_tasks project) - for now it only validates workflow.yaml is safe (exists, gitignored if it ever does carry a literal key, no bare api_key literal). Actually launching a session via uv run --project vendor/stokowski is deliberately deferred to a follow-up.
• Removes the lc escript target - it never actually worked once exqlite (a NIF-backed dep) was added, since NIFs can't load from inside an escript archive, and nothing in CI or docs ever exercised it.
• Documents mix run as the supported way to invoke lc locally, plus a standing rule to dogfood lc itself for Linear access rather than an MCP server or other integration skill (app/usage-rules.md, indexed from AGENTS.md).
• Closes Add stokowski framework for agent orchestration #100. Mirrored as CRY-38 in Linear's "Linear CLI" project.

Follow-ups (not in this PR)

• Wire mix stokowski up to actually start a session once the uv run invocation has been tested end-to-end.
• Upstream PR to Sugar-Coffee/stokowski: WorkflowConfig.agent_env() in stokowski/config.py checks the raw tracker.api_key string instead of the resolved value (unlike ProjectConfig.agent_env()) - on a bad $VAR reference it silently clobbers an otherwise-correct LINEAR_API_KEY env var with an empty string. The README setup guide (step 3) and single-project config reference also only show the bare-literal api_key pattern.

Test plan

• mix test in app/ - 227/227 passed
• mix format --check-formatted clean in both app/ and the root repo_tasks project
• mix usage_rules.sync --check clean in app/
• Verified workflow.yaml/.ai/prompts/*.md contain no literal secrets before committing (only commented $LINEAR_API_KEY examples)
• Dogfooded lc itself (via mix run, no MCP) to create CRY-38 in Linear's "Linear CLI" project, confirming the documented mix run invocation actually works end-to-end

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR vendors the Stokowski agent-orchestration framework (as a submodule) and introduces a repo-level Stokowski workflow + prompt templates, along with a new mix stokowski task intended to validate that the checked-in workflow.yaml is safe (no literal Linear API key). It also removes the unused/broken lc escript target and updates repo guidance to dogfood lc via mix run instead of using external Linear integrations.

Changes:

• Add a checked-in workflow.yaml and .ai/prompts/*.md templates to define a Linear-driven agent workflow.
• Add mix stokowski (repo_tasks) and a minimal test scaffold for it; add Python 3.14.1 to mise.toml for Stokowski.
• Remove the lc escript target and update documentation/comments to reflect mix run/release usage.

Reviewed changes

Copilot reviewed 16 out of 18 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
workflow.yaml	Adds the shared Stokowski workflow configuration for this repo.
.ai/prompts/global.md	Global prompt preamble for all agent stages.
.ai/prompts/investigate.md	Investigation-stage prompt template.
.ai/prompts/implement.md	Implementation-stage prompt template.
.ai/prompts/review.md	Code-review-stage prompt template.
.ai/prompts/merge.md	Merge-stage prompt template.
lib/mix/tasks/stokowski.ex	Introduces mix stokowski safety validation task for workflow.yaml.
test/mix/tasks/stokowski_test.exs	Adds initial ExUnit coverage for the new Mix task.
mise.toml	Pins Python to support running vendored Stokowski.
.gitmodules	Adds vendor/stokowski submodule entry.
app/mix.exs	Removes the escript target for lc.
app/.gitignore	Removes the ignore entry for the old lc escript artifact.
app/usage-rules.md	Documents dogfooding lc via mix run and avoiding Linear MCP/skills.
app/lib/linear_cli/application.ex	Updates comments to reflect Burrito release vs mix run (no escript).
app/lib/linear_cli/oban_repo.ex	Updates comments to remove escript references.
AGENTS.md	Indexes the new dogfooding rule from app/usage-rules.md.

Suppressed comments (2)

lib/mix/tasks/stokowski.ex:38

• mix stokowski currently requires workflow.yaml to be gitignored, but this PR also adds and tracks workflow.yaml in the repo. That makes mix stokowski fail in the normal (tracked) case and contradicts the PR description/intent (checked-in workflow with no literal key). Drop the unconditional gitignore gate; the existing api_key literal check already prevents committing a secret.

    unless gitignored?(workflow) do
      Mix.raise(
        "#{workflow} is not gitignored - it can hold a live Linear API key, add it to .gitignore before continuing"
      )
    end

lib/mix/tasks/stokowski.ex:61

• After removing the unconditional gitignore check in run/1, gitignored?/1 becomes unused. Keeping an unused private function will introduce warnings and can hide real unused-code issues later; it should be removed (or only added back when it’s actually needed).

  defp gitignored?(path) do
    match?({_, 0}, System.cmd("git", ["check-ignore", "-q", path], stderr_to_stdout: true))
  end

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