Forms: Add step names and dots style to progress indicator

[lezama]

Summary

Enhances the form progress indicator block with new display options and improved functionality:

• Block Styles: Adds "Line" (default) and "Dots" style variations
• Step Names Toggle: Adds setting to show/hide custom step names for both styles
• Server-side Rendering: Implements PHP rendering using block context and Tag Processor
• Block Context Integration: Uses WordPress block context system to share step data between form and progress indicator blocks
• Fallback Support: Gracefully falls back to parsing post content when context data is unavailable

Features

Line Style (Default)

• Shows traditional progress bar with optional step names below
• Step names appear as labels positioned along the progress line

Dots Style

• Shows circular dots representing each step
• Active steps are highlighted with the current color
• Step names appear below each dot when enabled

Settings Panel

• Toggle to show/hide step names for both styles
• Works with custom step labels set in form step blocks

Technical Implementation

• Uses providesContext/usesContext for proper data sharing between blocks
• Server-side rendering ensures SEO-friendly output and better performance
• CSS-based styling with proper theme color integration
• JavaScript handles active state updates during step navigation

Test plan

• Create a multi-step form with custom step labels
• Add progress indicator block
• Test line style with step names on/off
• Test dots style with step names on/off
• Verify step names show custom labels, not generic ones
• Test on frontend with step navigation
• Verify active states update correctly

[github-actions]

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[github-actions]

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 6 files. Only the first 5 are listed here.

File	Coverage	Δ%	Δ Uncovered
projects/packages/forms/src/contact-form/class-contact-form-plugin.php	435/1232 (35.31%)	-1.65%	55 💔
projects/packages/forms/src/blocks/form-progress-indicator/edit.js	0/15 (0.00%)	0.00%	6 💔
projects/packages/forms/src/blocks/contact-form/edit.js	0/216 (0.00%)	0.00%	3 ❤️‍🩹
projects/packages/forms/src/modules/form-progress-indicator/view.js	0/8 (0.00%)	0.00%	2 ❤️‍🩹
projects/packages/forms/src/blocks/form-progress-indicator/save.js	0/4 (0.00%)	0.00%	1 ❤️‍🩹

Full summary · PHP report · JS report

_{If appropriate, add one of these labels to override the failing coverage check: Covered by non-unit tests Use to ignore the Code coverage requirement check when E2Es or other non-unit tests cover the code Coverage tests to be added later Use to ignore the Code coverage requirement check when tests will be added in a follow-up PR I don't care about code coverage for this PR Use this label to ignore the check for insufficient code coveage.}