ci(docs): make the link checker scan the current SCF plan

[karagozemin]

Problem

pnpm docs:check-links fails on the current branch because the link checker still tries to scan the removed docs/SCF_PLAN.md. The maintained document is docs/SCF_TRANCHE_PLAN.md.

Task

Update the link checker source list to scan the maintained SCF tranche plan. Do not restore the deleted document and do not hide the failure with an allowlist entry.

Acceptance criteria

• pnpm docs:check-links passes.
• The maintained SCF tranche plan is included in local-link validation.
• No unrelated documentation or formatting changes are included.

Suggested implementation prompt

Fix this issue from the current main branch. Update the documentation link checker to scan the maintained SCF tranche plan instead of the deleted legacy plan, run pnpm docs:check-links, and keep the diff strictly scoped.

[adelekevictor12]

Hello maintainer, i can fix this issue

[adelekevictor12]

Hello maintainer, i can fix this issue

[grantfox-oss]

🦊 GrantFox — @adelekevictor12 has been assigned to this issue!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #235)
2. Your PR will be reviewed by the Sub-Rosa-Issue maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox!

@adelekevictor12's PR #269 was approved and merged by @karagozemin.

🏆 @adelekevictor12: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (707 total points). Track your full progress on GrantFox.

👏 Great work, @adelekevictor12! Keep contributing to Sub-Rosa-Issue.