fix: lower the accidental opentelemetry-api floor in the otel extra

[bagowix]

Summary

pyproject.toml declared otel = ["opentelemetry-api>=1.43.0"]. That floor
was never a requirement of the code: it arrived as a side effect of a routine
dependency bump (3d664ad, #7) that moved the dev pin, the extra's lower bound
and the extras-min CI pin together. Git history shows the extra's floor was
originally >=1.20.0 at introduction — the bump silently raised a
compatibility statement while only intending to bump what we develop against.

OTelEventListener only calls metrics.get_meter, Meter.create_histogram
and Meter.create_counter, API that has been stable for years. Verified
locally: tests/test_otel.py passes unchanged against
opentelemetry-api==1.20.0.

The cost to adopters was real: opentelemetry-distro/SDK releases pin the
whole OTel stack to one API version, so the stale floor forced anyone on an
older distro to choose between upgrading their entire OTel stack and dropping
interlock-cb[otel] — for a listener that would have worked fine.

Changes

• Lower the otel extra floor back to opentelemetry-api>=1.20.0 and pin
  .github/workflows/ci.yml's extras-min job to the same version, so CI
  proves it on 3.11.
• Keep the dependency-groups.dev pin at the current version — development
  continues against the latest.
• Document the rule in CONTRIBUTING.md: an extra's floor is a compatibility
  statement, not a dev pin, and a routine bump must never carry both together.
• CHANGELOG.md entry under [Unreleased] → Changed.

Extras floor audit

Checked git history for every other extra (httpx, httpx2, fastapi,
redis, litestar, tenacity, requests, aiohttp): each floor was set
once at introduction (in the PR that added the integration) and has never
been touched by a routine bump commit. None of them are equally accidental.

Checklist

• Tests added or updated (suite stays at 100% coverage) — n/a, no library
  code changed; tests/test_otel.py verified against the new floor
• uv run ruff format --check and uv run ruff check pass
• uv run mypy, uv run pyright and uv run pyrefly check pass — n/a,
  no Python source changed
• Docs updated (docs/) for user-facing changes — n/a, no docs/ page
  references the version number
• CHANGELOG.md [Unreleased] updated
• Commits follow Conventional Commits

Related issues

Closes #138

Changed

• Lower the otel extra compatibility floor to opentelemetry-api>=1.20.0.
• Test opentelemetry-api==1.20.0 in extras-min while retaining the current development pin.
• Document compatibility floors and development pins in CONTRIBUTING.md.
• Audit other extras and confirm that their floors are intentional.

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Review details

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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Run ID: 77b6389b-1dba-451a-83c5-26a81f65fd61

📥 Commits

Reviewing files that changed from the base of the PR and between 75e6370 and 2a7d548.

📒 Files selected for processing (2)

• docs/guides/observability.md
• docs/llms-full.txt

Walkthrough

The otel optional dependency floor is lowered to opentelemetry-api>=1.20.0. The minimum-version CI job tests that version. The changelog and contributor guidance document the compatibility-floor policy.

Changes

OpenTelemetry compatibility floor

Layer / File(s)	Summary
Lower floor and minimum-version validation .github/workflows/ci.yml, pyproject.toml	The otel extra now requires opentelemetry-api>=1.20.0. The extras-min CI job installs opentelemetry-api==1.20.0.
Document the compatibility-floor policy CHANGELOG.md, CONTRIBUTING.md	The changelog records the lower floor and CI coverage. Contributor guidance distinguishes compatibility floors from development pins and requires CI updates for intentional floor increases.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Suggested labels: dependencies, github_actions

🚥 Pre-merge checks | ✅ 8 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docs And Llm Mirror	⚠️ Warning	The PR changes the public OTel integration's supported dependency floor, but HEAD changes no docs/ page and does not regenerate docs/llms-full.txt.	Update docs/guides/observability.md with the supported otel floor, then regenerate docs/llms-full.txt and commit both files.

✅ Passed checks (8 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title uses the required Conventional Commit format, imperative wording, lower case, and a 67-character length.
Linked Issues check	✅ Passed	The changes satisfy the linked issue: they lower the floor, update CI, preserve the development pin, document the rule, audit extras, and add the changelog entry.
Out of Scope Changes check	✅ Passed	All reviewed changes support the linked issue objectives; no unrelated code or documentation changes are present.
Zero-Dependency Core	✅ Passed	No files under interlock changed; project dependencies remains []; interlock/init.py has no imports or re-exports from interlock.integrations.
Changelog Entry	✅ Passed	CHANGELOG.md adds a bullet under [Unreleased] → Changed describing the lower otel floor and the adopter impact.
Tests Accompany Behaviour Change	✅ Passed	The PR changes only workflow, documentation, pyproject.toml, and uv.lock files; no .py file under interlock/ changed, so the check's first PASS condition applies.
Public Api Surface	✅ Passed	The PR changes no lines in interlock/init.py or interlock/pipeline.py; the parent-to-HEAD diff for both public API files is empty.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/138-otel-extra-floor

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[codspeed-hq]

Merging this PR will not alter performance

✅ 24 untouched benchmarks

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_{Comparing fix/138-otel-extra-floor (2a7d548) with main (677fb37)}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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