feat(run-environment): add CircleCI provider for GitHub repositories

[fargito]

Add a CircleCI run environment, for repositories hosted on GitHub.

The build runs on CircleCI while commits and pull requests live on GitHub, so the run is reported
against the GitHub commit and pull request. Detection is CIRCLECI=true, and the repository comes
from CIRCLE_REPOSITORY_URL.

CircleCI also builds Bitbucket and GitLab repositories, so the remote's domain is checked and
anything but github.com is rejected with an error naming the domain found. That domain is the
only signal available at runtime: pipeline.project.type is a pipeline value, interpolated when
the config is compiled, so it never reaches the job as an environment variable.

Two things worth a look:

• No commit hash override. CircleCI checks out the associated commit rather than a synthetic
  merge ref, so reading git HEAD already yields CIRCLE_SHA1.
• runId is CIRCLE_WORKFLOW_ID, shared by every job and every parallel container of a
  workflow. The per-job CIRCLE_WORKFLOW_JOB_ID would split one workflow into unrelated runs.
  runPartId is {CIRCLE_JOB}-{CIRCLE_NODE_INDEX}, to stay unique along both fan-out axes.

baseRef is left empty, as CircleCI exposes no base-branch variable. Pull request uploads need a
server-side change that is not released yet; push events are unaffected.

Uploads authenticate with a static CODSPEED_TOKEN. Minting OIDC tokens instead is #482, stacked
on top.

Refs COD-2995
Refs COD-3262

[greptile-apps]

Greptile Summary

Adds CircleCI support for GitHub-hosted repositories.

• Detects CircleCI jobs and derives repository, ref, event, workflow, job, and parallel-node metadata from CircleCI environment variables.
• Adds CircleCI-specific logging and static-token authentication guidance.
• Registers CircleCI in provider selection and upload-error handling.

Confidence Score: 5/5

The PR appears safe to merge with respect to the eligible follow-up findings.

No blocking failure remains from the previous logger thread, because direct stdout output is required inside the logging sink and matches the repository's other logger backends.

Important Files Changed

Filename	Overview
src/run_environment/circleci/provider.rs	Implements CircleCI detection, GitHub repository validation, event metadata, static-token enforcement, and workflow run-part identity.
src/run_environment/circleci/logger.rs	Adds a CircleCI logging sink with colored headings and level-aware output consistent with the repository's logger implementations.
src/run_environment/mod.rs	Registers CircleCI in provider detection before the local fallback.
src/run_environment/interfaces.rs	Adds the serialized CircleCI run-environment variant.
src/upload/uploader.rs	Provides CircleCI users the static-token authentication hint for unauthorized uploads.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  Env["CircleCI environment variables"] --> Detect["Detect CIRCLECI=true"]
  Detect --> Validate["Parse and validate GitHub repository"]
  Validate --> Metadata["Build run-environment metadata"]
  Validate --> Part["Build workflow/job/node run-part identity"]
  Metadata --> Upload["Upload benchmark profile"]
  Part --> Upload
  Token["CODSPEED_TOKEN"] --> Upload

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_{Reviews (4): Last reviewed commit: "feat(run-environment): add CircleCI prov..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 17 untouched benchmarks

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_{Comparing feat/circleci-run-environment (4e52cfa) with main (97a789a)}

[adriencaccia]

As seen together, if this is not needed anymore, let's remove the field