feat(tutorial): Track 1 (YAML/OpenAPI) example files — maritime red-thread

[eskenazit]

Related Issue

Closes #49

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What does this PR do?

Adds the Track 1 (YAML / OpenAPI) tutorial example files under
examples/tutorial/track-1-yaml/, plus the tuto_writer agent that authored them.

These are the runnable artifacts the public Shipyard tutorial page links to. The maritime
red-thread example (a Modern Maritime Registry API scoped to /ships, /ships/{imo_number}
and /crew) grows step by step across seven OpenAPI documents:

• step-1-openapi.yml … step-7-openapi.yml — the seven progressive OpenAPI specs.
• openapi-ruleset.yml — the custom Polychro ruleset used from Step 3 on.
• openapi-schema.json — the JSON Schema referenced by Step 4.
• .polychro.yml — the project config used by Step 4.
• functions/operation-id-unique.js — the polyglot custom rule used in Step 6.
• EXPECTED-OUTPUT.md — the exact CLI output for every step, verified against
  polychro 1.0.0-beta1-SNAPSHOT.
• LIMITATIONS.md — two known beta1 gaps documented (not fixed) and explicitly out of scope:
  • §5 — non-string-key false positive on a quoted "200" key.
  • §6 — Step 4's config.json-schema in .polychro.yml is not consumed yet.

Every diagnostic and exit code documented here was produced by running the real beta1 CLI —
nothing is hand-written.

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⚠️ Merge order — this PR must merge BEFORE Shipyard PR #150

The public tutorial page in naftiko/shipyard#150
links to these files on main:

• https://github.com/naftiko/polychro/blob/main/examples/tutorial/track-1-yaml/…
• https://raw.githubusercontent.com/naftiko/polychro/main/examples/tutorial/track-1-yaml/…

Those links only resolve once this PR is merged. Merge this PR first, then Shipyard #150.
Merging Shipyard #150 first would publish a page with broken file links.

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Tests

No automated tests in this PR — it adds example fixtures and documentation only.

The example outputs were validated manually against the real 1.0.0-beta1-SNAPSHOT CLI
(classpath run from examples/tutorial/track-1-yaml/); the produced diagnostics, exit codes and
the --format agent JSON match EXPECTED-OUTPUT.md exactly.

A follow-up under #49 will add a JUnit harness that lints each example and asserts its
diagnostics, wired into CI.

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Checklist

• CI is green (build + tests)
• Rebased on latest main
• Small and focused — one concern per PR
• Commit messages follow Conventional Commits
• Apache 2.0 license header present on any new Java file (none added — examples + agent only)

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Agent Context (optional)