ci: Compact first-time contributor welcome and stop issue-link pollution

[Ma77Ball]

What changes were proposed in this PR?

Reworks the first-time-contributor welcome comment posted by welcome-first-time-contributor.yml.

• Rewrote the welcome message: an opening pointer to starter-task issues for newcomers, plus clearer full-sentence guidance for the three comment-command groups (issues, sub-issues, pull requests).
• Wrapped every issue reference in inline code so GitHub no longer autolinks the examples (these previously created cross-reference backlinks into real issues each time the welcome fired) and switched the examples to the self-referential #5166 and #5222.
• Moved the message body out of the workflow .yml and into .github/welcome-first-time-contributor.txt, read at runtime via a sparse checkout and rendered by substituting {{author}}, {{owner}}, and {{repo}}.
• Excluded that .txt file from the ci label in labeler.yml, so a wording-only edit no longer maps to every build stack and skips the full CI run.

The rendered message a first-time contributor now sees:

👋 Thanks for your first contribution to Texera, @<author>!

If you're looking for a good place to start, browse issues labeled starter-task; they're scoped to be approachable for newcomers.

You can drive common housekeeping yourself by commenting one of these commands on its own line:

• Issues. Comment /take to assign an open issue to yourself, or /untake to release it. You can find unclaimed work with the search filter is:issue is:open no:assignee.
• Sub-issues. To link issues into a parent/child hierarchy, comment /sub-issue #5166 #5222 on the parent to attach those children (or /unsub-issue #5166 #5222 to detach them). From a child issue, comment /parent-issue #5166 to set its parent, or /unparent-issue to clear it (the current parent is detected automatically). References may be written as #5166 or as a bare 5166; cross-repository references are not supported.
• Pull requests (author only). Comment /request-review @user to request a review from someone, or /unrequest-review @user to withdraw that request.

Each command must match exactly: /take this will not work, only /take does. For the full contribution flow, see CONTRIBUTING.md.

Any related issues, documentation, or discussions?

Closes: #5315

How was this PR tested?

• Cross-referenced every command claim against comment-commands.yml for accuracy.
• Simulated the runtime substitution locally (read the .txt, replaced the placeholders, prepended the idempotency marker) and confirmed the output matches the message above with no leftover placeholders.
• Confirmed via GitHub docs that #N inside inline code is not autolinked, and verified zero bare #N remain in the message body.

Was this PR authored or co-authored using generative AI tooling?

Co-authored with Claude Opus 4.8 in compliance with ASF

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.38%. Comparing base (07ca5d4) to head (37a25a6).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5317      +/-   ##
============================================
- Coverage     52.38%   52.38%   -0.01%     
+ Complexity     2484     2480       -4     
============================================
  Files          1070     1070              
  Lines         41359    41359              
  Branches       4441     4441              
============================================
- Hits          21666    21664       -2     
+ Misses        18427    18422       -5     
- Partials       1266     1273       +7     

Flag	Coverage Δ		*Carryforward flag
access-control-service	64.61% <ø> (ø)
agent-service	33.76% <ø> (ø)
amber	53.27% <ø> (-0.04%)	⬇️
computing-unit-managing-service	1.65% <ø> (ø)
config-service	56.06% <ø> (ø)
file-service	38.21% <ø> (ø)
frontend	46.94% <ø> (+0.02%)	⬆️
pyamber	90.72% <ø> (ø)
python	90.75% <ø> (ø)		Carriedforward from 07ca5d4
workflow-compiling-service	58.69% <ø> (ø)

*This pull request uses carry forward flags. Click here to find out more.

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[Ma77Ball]

/request-review @Yicong-Huang

[Yicong-Huang]

Approved with one comment inline.

[Yicong-Huang]

will wait for #5244, I believe some of the commands here is describing the action in that PR.

[Copilot]

Pull request overview

This PR refactors the first-time contributor welcome comment workflow to reduce noise and prevent GitHub issue auto-linking from creating unwanted cross-references, while making the message easier to edit without touching workflow logic.

Changes:

• Move the welcome message body out of .github/workflows/welcome-first-time-contributor.yml into .github/welcome-first-time-contributor.txt, and load it at runtime with placeholder substitution.
• Rewrite the welcome text to be shorter and wrap issue references in inline code to avoid autolink/backlink “pollution”.
• Update .github/labeler.yml to try to exclude wording-only edits of the template from applying the ci label.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/welcome-first-time-contributor.yml	Adds sparse checkout of the welcome template and renders the comment body from that template at runtime.
.github/welcome-first-time-contributor.txt	New standalone welcome message template with placeholders and non-autolinking examples.
.github/labeler.yml	Attempts to exclude the welcome template from the ci label so wording-only edits can skip full CI.

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[aglinxinyuan]

Update the PR description as well.

[Yicong-Huang]

Pr description is not accurate? I don't think we have labeler change in this PR. @Ma77Ball

[Ma77Ball]

It did have labeled changes as shown in the Copilot comment. I removed this as the effort to avoid a full CI run will require some trade-off (either direction we take).

[aglinxinyuan]

Pr description is not accurate? I don't think we have labeler change in this PR. @Ma77Ball

I left a comment for this one already.