Update Doc Handbook for Week 9-11

[Urvashi0109]

What type of PR is this:

/kind documentation

What this PR does / why we need it:

This PR improves the Late Steps (Weeks 9-11) - Prep for the Release section of the Docs Release Timeline handbook by updating documentation and the workflow for this critical phase of the release cycle with current practice followed.

Key updates:

• Added Total Time Estimates: Helps to better understand effort distribution and timeline alignment.
• Added and updated Action Items to All Subsections (Week 9–10)
• Messaging Template Improvements:
  - Introduced a dedicated folder for messaging templates to centralize and organize all communication templates.
  - Updated the Late Steps (Weeks 9-11) - Prep for the Release section with messaging template practice.
• Final Release Notes Preparation (Critical Update):
  - Added and expanded a detailed section for Final Release Note preparation.
  - Documented the step-by-step process currently being followed.
• Updated Table of Contents links for Late Steps (Weeks 9-11) - Prep for the Release section to match the renamed section headings

Which issue(s) this PR fixes:

Special notes for your reviewer:

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Urvashi0109 / name: Urvashi Choubey (2c10b6b, 4f7182d, ab306dc, dae38cc, db6f2a7)

[Urvashi0109]

/assign @katcosgrove

[Copilot]

Pull request overview

This PR updates the Docs Release Timeline handbook for Weeks 9–11 (“Late Steps”) and introduces reusable Slack/meeting messaging templates to reflect current release practices.

Changes:

• Added a more detailed “Late Steps (Weeks 9–11)” workflow, including time estimates, action items, and a detailed final release notes preparation process.
• Introduced dedicated messaging templates for coordinating with SIG Docs and verifying kubeadm documentation with SIG Cluster Lifecycle.
• Updated the Release Timeline table of contents to match the revised Late Steps subsections.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
release-team/role-handbooks/docs/Release-Timeline.md	Updates Late Steps (Weeks 9–11) content and TOC to reflect current process and templates.
release-team/role-handbooks/docs/templates/sig-docs-coordination.md	Adds a reusable coordination message template for SIG Docs release-day support + generated docs status.
release-team/role-handbooks/docs/templates/sig-cluster-lifecycle-verification.md	Adds a reusable verification message template for SIG Cluster Lifecycle (kubeadm) docs readiness.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Urvashi0109
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