ci: add lychee broken link validation CI for docs

[vanshika2720]

What this PR does:
Introduces an automated broken link and asset checker CI pipeline for the docs/ directory using Lychee.

1. GitHub Actions Workflow (.github/workflows/docs-link-checker.yaml):
   • DX-Optimized PR Checking: On pull requests, it uses a secure native git diff compared to origin/master to isolate and scan only modified markdown files. This guarantees developers are not blocked by legacy, historical broken links.
   • Thorough master Audits: On push to master, it executes a full-health check across all active documentation pages (docs/content/**/*.md and docs/README.md).
2. Lychee Ruleset Configuration (lychee.toml):
   • Configures root_dir = "docs/static" to resolve root-relative paths like /images/... to physical local files.
   • Bypasses local/private URLs and dynamic Hugo page-routing links.
   • Adds resilience to network rate limits and DDoS protectors (e.g. Cloudflare) by treating common false-positive HTTP codes (400, 403, 429) as acceptable.

Why we need it:
Manually catching 404 links and broken image assets in documentation is highly error-prone. This CI pipeline:

• Automatically prevents new broken links from being merged.
• Provides a fast, frictionless experience for developers (zero-dependency, only processes their specific changed files in PRs).
• Protects docs quality without introducing pipeline noise.

Does this PR introduce a user-facing change?:
No

[vanshika2720]

@rahulshendre @khanhtc1202 @eeshaanSA

[Ayushmore1214]

@vanshika2720 there is already a assignee on this specific idea and a PR has been already raised by @zyzzmohit #6570 no worries at all this is your first time here, mistake often happens, lets do one thing you can join tomorrow's community meet along with @zyzzmohit we can discuss which option works better, see you in the meet tomorrow :)

[vanshika2720]

@Ayushmore1214 Yeah, I saw that one, but it looked stale so I opened this instead.

[zyzzmohit]

Hi @vanshika2720 thanks for putting this together your approach with the PR diff scanning looks really interesting I've been actively working on #6570 for this issue, but I understand why it might have seemed inactive if there haven't been recent commits
and @Ayushmore1214 thanks for the ping I will absolutely join the community meet tomorrow so we can compare the approaches and figure out the best solution for PipeCD See you both there :)

[Ayushmore1214]

@Ayushmore1214 Yeah, I saw that one, but it looked stale so I opened this instead.

You might have asked the owner of the PR if the PR is still active or not, but no worries keep in mind from next time

[Ayushmore1214]

Hi @vanshika2720 thanks for putting this together your approach with the PR diff scanning looks really interesting I've been actively working on #6570 for this issue, but I understand why it might have seemed inactive if there haven't been recent commits and @Ayushmore1214 thanks for the ping I will absolutely join the community meet tomorrow so we can compare the approaches and figure out the best solution for PipeCD See you both there :)

Hi @zyzzmohit FYI the meet was today not tomorrow, no worries you can discuss the intent here

[github-actions]

This PR is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[vanshika2720]

@rahulshendre @mohammedfirdouss PTAL!!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 25.92%. Comparing base (6cc2b17) to head (29432ab).
⚠️ Report is 57 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6789      +/-   ##
==========================================
- Coverage   29.35%   25.92%   -3.43%     
==========================================
  Files         601      468     -133     
  Lines       64317    51726   -12591     
==========================================
- Hits        18880    13410    -5470     
+ Misses      43968    37217    -6751     
+ Partials     1469     1099     -370     

Flag	Coverage Δ
.	23.12% <ø> (ø)
.-pkg-app-pipedv1-plugin-analysis	?
.-pkg-app-pipedv1-plugin-ecs	?
.-pkg-app-pipedv1-plugin-kubernetes	58.37% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes_multicluster	?
.-pkg-app-pipedv1-plugin-scriptrun	?
.-pkg-app-pipedv1-plugin-terraform	?
.-pkg-app-pipedv1-plugin-wait	?
.-pkg-app-pipedv1-plugin-waitapproval	?
.-pkg-plugin-sdk	?
.-tool-actions-gh-release	?
.-tool-actions-plan-preview	?
.-tool-codegen-protoc-gen-auth	?

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