fix(ci): unbreak pr-review-confirm workflow YAML parsing

[tylerbutler]

Description

The `PR Review Confirm` workflow (introduced in #27107) fails to parse and produces zero jobs on every PR — GitHub reports "This run likely failed because of a workflow file issue" (e.g. run 24861202057). The Q&A step used three bash heredocs whose bodies were flush-left inside a `run: |` YAML block scalar; YAML terminated the scalar at the first unindented line, leaving the rest of the file unparseable.

This change:

• Extracts the Q&A prompt into `.github/prompts/pr-review-qa.md`, sibling to the existing reviewer prompts, using the repo's `VAR` placeholder convention.
• Adds a `render-qa-prompt` subcommand on `.github/scripts/pr_review_propose.py` that substitutes `REVIEWER_CONTEXT` and `REPLY` from environment variables (safe for multi-line values and arbitrary special characters) and opens the template as UTF-8.
• Replaces the heredoc block in the workflow with a single call to the new subcommand, and extends the step's sparse-checkout to include `.github/prompts`.
• Adds unit and CLI tests for the new subcommand alongside the existing `pr_review_propose.py` tests.

Reviewer Guidance

The review process is outlined on this wiki page.

[github-actions]

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Based on the diff (51 lines, 2 files), I've queued these reviewers:

• Correctness — logic errors, race conditions, lifecycle issues
• Security — vulnerabilities, secret exposure, injection
• API Compatibility — breaking changes, release tags, type design
• Performance — algorithmic regressions, memory leaks
• Testing — coverage gaps, hollow tests

Toggle checkboxes to adjust, then reply yes to start — or ask me anything!

[Copilot]

Pull request overview

Fixes the PR Review Confirm GitHub Actions workflow so it parses and runs correctly by moving the Q&A prompt into a dedicated prompt file and generating the final prompt safely at runtime.

Changes:

• Expand the workflow checkout sparse list to include .github/prompts.
• Replace the YAML-breaking heredoc construction with a Python-based placeholder substitution into a prompt template.
• Add a new .github/prompts/pr-review-qa.md template for the Q&A prompt.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/pr-review-confirm.yml	Updates checkout + replaces heredoc prompt assembly with template substitution.
.github/prompts/pr-review-qa.md	Adds the prompt template with __VAR__ placeholders for runtime substitution.

[Copilot]

The embedded Python passed to python3 -c is indented inside the single-quoted string. Those leading spaces become part of the Python source and will cause IndentationError: unexpected indent when this step runs. Please rewrite this so the -c code has no leading indentation (e.g., a single-line -c with semicolons, or generate/dedent the script content before execution). Also consider opening the template with an explicit encoding='utf-8' to avoid locale-dependent behavior on runners.

Suggested change

	python3 -c '
	import os, sys
	tmpl = open(sys.argv[1]).read()
	tmpl = tmpl.replace("__REVIEWER_CONTEXT__", os.environ["REVIEWER_CONTEXT"])
	tmpl = tmpl.replace("__REPLY__", os.environ["REPLY"])
	sys.stdout.write(tmpl)
	' .github/prompts/pr-review-qa.md > /tmp/qa-prompt.md
	python3 -c 'import os, sys; tmpl = open(sys.argv[1], encoding="utf-8").read(); tmpl = tmpl.replace("__REVIEWER_CONTEXT__", os.environ["REVIEWER_CONTEXT"]); tmpl = tmpl.replace("__REPLY__", os.environ["REPLY"]); sys.stdout.write(tmpl)' .github/prompts/pr-review-qa.md > /tmp/qa-prompt.md

[github-actions]

🔗 No broken links found! ✅

Your attention to detail is admirable.

linkcheck output

> fluid-framework-docs-site@0.0.0 ci:check-links /home/runner/work/FluidFramework/FluidFramework/docs
> start-server-and-test "npm run serve -- --no-open" 3000 check-links

1: starting server using command "npm run serve -- --no-open"
and when url "[ 'http://127.0.0.1:3000' ]" is responding with HTTP status code 200
running tests using command "npm run check-links"


> fluid-framework-docs-site@0.0.0 serve
> docusaurus serve --no-open

[SUCCESS] Serving "build" directory at: http://localhost:3000/

> fluid-framework-docs-site@0.0.0 check-links
> linkcheck http://localhost:3000 --skip-file skipped-urls.txt

Crawling...

Stats:
  287071 links
    1898 destination URLs
    2148 URLs ignored
       0 warnings
       0 errors