feat(tier-check): support configurable label taxonomy and aliases for Tier 1 repo checks

Is your feature request related to a problem? Please describe.

The MCP SDK Tiering specification (SEP-1730 / docs/community/sdk-tiers.mdx) requires specific labels for issue triage (bug, enhancement, question), status (needs confirmation, needs repro, ready for work, good first issue, help wanted), and priority (P0–P3).

Currently, tier-check enforces these through exact hardcoded string matches:

• Matches lowercase names strictly against TYPE_LABELS, STATUS_LABELS, and PRIORITY_LABELS.
• Hardcodes labels: 'P0' when querying GitHub's API to calculate critical issue resolution times.

Many organizations and SDK ecosystems (e.g. Google/DevRel, cloud providers, and established OSS projects) use namespaced labels like priority: p0, type: bug, and status: waiting for response to support organization-wide issue taxonomies, automation bots, and issue-mirroring bridges (e.g., Jira, Google Issue Tracker).

Even when an SDK repository fully adheres to the required semantic taxonomy and respects the triage/P0 SLAs, tier-check fails due to exact string mismatch. Forcing these repos to adopt bare strings creates unnecessary migration friction for maintainers seeking Tier 1 / Tier 2 certification.

Describe the solution you'd like.

Allow tier-check to recognize configurable label aliases or mappings so repositories can pass tier checks while preserving their established label conventions.

1. Configuration Mechanism:
   Support an optional label alias mapping, configured either via:

   • A repository-level config file (e.g., .github/mcp-conformance.json or .mcp/tier-check.json).
   • The built-in SDK config in src/sdk-runner/known-sdks.ts (or via a CLI flag like --labels-config).

   Example configuration:

   {
     "labels": {
       "aliases": {
         "bug": ["type: bug"],
         "enhancement": ["type: feature request"],
         "question": ["type: question"],
         "needs confirmation": ["status: feedback wanted", "status: investigating"],
         "needs repro": ["status: waiting for response", "needs more info"],
         "ready for work": ["ready for work", "needs work"],
         "help wanted": ["status: help wanted", "help wanted"],
         "P0": ["priority: p0"],
         "P1": ["priority: p1"],
         "P2": ["priority: p2"],
         "P3": ["priority: p3"]
       }
     }
   }
   

2. Evaluation in checkLabels:
   When evaluating whether a required label is present, check if the repo contains the standard label name or any of its configured aliases.

3. Evaluation in checkP0Resolution:
   Update checkP0Resolution to query the configured P0 label (e.g., priority: p0 instead of the hardcoded 'P0'), ensuring that P0 resolution metrics reflect the repository's actual critical issues.

4. Default Behavior:
   If no mapping is provided, retain the exact current behavior with zero breaking changes.

Describe alternatives you've considered

1. Renaming labels in each SDK repository:
   Breaks existing workflows, bot automation, and internal issue-sync tooling across repos that rely on structured label prefixes (priority:*, type:*, status:*).

2. Duplicate labels (e.g., both P0 and priority: p0):
   Creates contributor confusion, label clutter, and requires maintainers to double-tag every issue to satisfy both external checks and internal automations.

3. Relying solely on GitHub Issue Types:
   checkLabels already supports GitHub Issue Types for bug/enhancement/question, but GitHub Issue Types do not cover status or priority (P0–P3), leaving the main gap unaddressed.

4. Simple prefix-stripping:
   While some differences are purely prefix/case conventions (e.g. priority: p0 vs P0, type: bug vs bug), many existing repos use established semantic synonyms for the same triage stages:

   • enhancement ➔ type: feature request
   • needs confirmation ➔ status: feedback wanted or status: investigating
   • needs repro ➔ status: waiting for response or needs more info
   • ready for work ➔ needs work

   Supporting a 1-to-many alias dictionary ensures existing repositories with mature workflows don't have to break internal automations or rename established labels.

Additional Context

• We are seeing this while preparing the MCP Toolbox repositories for Tier 1 conformance. All required triage and priority categories are tracked, but naming conventions follow standard namespaced prefixes (e.g., priority: p0, status: feedback wanted).
• We are happy to submit a PR to implement this alias support in src/tier-check/ if this approach aligns with the team.

Read docs/community/sdk-tiers.mdx and the tier-check implementation under src/tier-check/, focusing on checkLabels and checkP0Resolution; compare how src/sdk-runner/known-sdks.ts currently supplies SDK configuration. Confirm the chosen alias/configuration path preserves exact current behavior when absent, recognizes configured aliases, and uses the configured P0 label for resolution metrics.