Add OSS suitability checks to PM backlog review

[markheydon]

Summary

• add OSS suitability classification to PM workflow rules
• run OSS suitability checks during /pm-backlog-review only
• add scripts/Export-OssSuitabilityAudit.ps1 for repo-local OSS asset auditing
• update PM prompt/agent/docs to reflect public-by-default OSS with private excluded and explicit opt-out support

Included changes

• update participation rules and OSS override guidance
• update backlog review prompt with OSS audit step and output expectations
• update PM operating model and prompt reference docs
• add how-to and reference updates for OSS suitability behaviour

Notes

• checks are informational and do not block normal backlog review
• sponsorship setting is represented by .github/FUNDING.yml presence

[Copilot]

Pull request overview

This PR extends the PM workflow to classify repositories for OSS suitability and to report (informational) gaps in repo-local community health assets during /pm-backlog-review, with opt-out support via participation overrides.

Changes:

• Adds an OSS suitability rule and OSS Override metadata to plan/REPO_PM_PARTICIPATION.md (public-by-default, private excluded, explicit public opt-out).
• Updates /pm-backlog-review prompt and Backlog Manager agent guidance to run and report OSS suitability checks (repo-local assets only).
• Adds a PowerShell audit script to generate CSV/Markdown reports for OSS suitability across repos, and updates docs to reflect the new behaviour.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
scripts/Export-OssSuitabilityAudit.ps1	New repo-local OSS asset audit script emitting CSV and optional Markdown.
plan/REPO_PM_PARTICIPATION.md	Defines OSS suitability evaluation order and adds OSS Override column to Active Overrides.
plan/OPERATING_MODEL.md	Documents OSS suitability audit as part of /pm-backlog-review in PM Mode.
docs/reference/repo-priorities.md	Notes participation file now carries OSS override metadata for backlog review.
docs/reference/pm-prompts.md	Updates /pm-backlog-review description and adds OSS override behaviour notes.
docs/how-to/change-repo-priority.md	Adds steps/tips for OSS override usage (backlog-review only).
.github/prompts/pm-backlog-review.prompt.md	Adds OSS classification rules, audit step, and findings section; includes repo visibility in repo listing.
.github/agents/pm-backlog-management.agent.md	Extends agent rules to parse OSS Override and scope OSS checks to backlog review only.