feat: remove milestone countdown alert banner

[Copilot]

The fixed-position top banner that appeared ~2 minutes before a milestone crossing was visually intrusive without adding meaningful value.

Changes

• src/js/19-milestone-alert.js: Removed countdown banner logic (MILESTONE_ALERT_THRESHOLD_SECS, banner DOM queries, threshold window display/update). Retained the milestone flash overlay (the modal dialog triggered on actual crossing) and the witness badge award.
• index.html: Removed #milestone-alert-banner element and its comment.
• styles/social.css: Removed .milestone-alert-banner, .milestone-alert-icon, .milestone-alert-msg, .milestone-alert-countdown, @keyframes alert-slide-down, @keyframes countdown-tick, and their reduced-motion/responsive overrides.

Summary by CodeRabbit

• Refactor
  • Removed the milestone countdown alert banner and associated styles and animations
  • Alert presentation now uses a flash overlay effect

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: c4aa087a-efb3-4bda-9751-5f32ebed1bac

📥 Commits

Reviewing files that changed from the base of the PR and between a0b3ce4 and fe317ee.

📒 Files selected for processing (5)

• index.html
• script.js
• src/js/19-milestone-alert.js
• styles.css
• styles/social.css

💤 Files with no reviewable changes (2)

• index.html
• styles/social.css

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📝 Walkthrough

Walkthrough

Fool, listen up! This change removes the milestone countdown alert banner functionality from the entire application. The banner UI elements, JavaScript countdown logic, and associated CSS styling are all stripped out, leaving only the flash-on-crossing overlay behavior for milestone achievements.

Changes

Cohort / File(s)	Summary
Milestone Alert Banner Removal index.html, styles/social.css	Removed the complete milestone countdown alert banner markup and styling, including fixed positioning, gradient backgrounds, slide-down animations, and countdown tick effects. No alternate UI is introduced.
Milestone Alert Logic Refactor src/js/19-milestone-alert.js	Eliminated threshold-based alert window logic; checkMilestoneAlert() now only triggers a one-time flash overlay and witness badge when a milestone is crossed (secsToNext <= 0). Removed all banner hide/show operations and DOM element dependencies.

Estimated Code Review Effort

🎯 2 (Simple) | ⏱️ ~10 minutes

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I pity the fool who leaves dead code hanging around! These changes are straightforward removals and simplifications across three related files. The refactored JavaScript logic is direct—checking milestone crossing and triggering the flash, no more banner shenanigans. Homogeneous pattern of cleanup makes it fool's work to review, sucka!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: remove milestone countdown alert banner' directly and accurately summarizes the main change—removal of the countdown alert banner component across multiple files (HTML, JavaScript, CSS).
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch copilot/remove-five-min-to-midnight-banner

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[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (fd1cb0d) to head (205e6dd).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #78   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          233       233           
  Branches       107       107           
=========================================
  Hits           233       233           

Flag	Coverage Δ
unit	100.00% <ø> (ø)

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[nitrocode]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved in 205e6dd. The conflict was caused by main (#80) removing generated files (script.js, styles.css, changelog-data.js, etc.) from git tracking via .gitignore. The merge commit removes those files from this branch to match, and all 253 unit tests still pass.