Replace Singer with Creative Muse and add staged Rednote workflow

[Angnuo (angnuoli)]

Description

Replace the narrow Singer persona with Creative Muse, a specialist that moves Rednote projects through reusable topic-discovery, sourced material-kit, and publish-ready visual-package stages.

Related Issue

N/A

Changes

• Replace Singer with Creative Muse across the agent catalog, localized UI, artwork, installer carousel, persona workspace, and legacy-agent migration
• Add three connected starter tasks: discover five sourced ideas, build the selected idea's material kit, and generate the final Rednote package
• Add the rednote-publisher skill with deterministic 3:4 cover/card rendering and strict stage/package validation
• Install rednote-publisher on demand only when Creative Muse is added; keep it out of the base managed-skill install and other agents' default allowlists
• Add transactional install/remove/startup reconciliation, exact integrity-snapshot handling, rollback protection, and preservation of modified skills and user workspaces
• Update Hero Scenario and managed/agent-owned skill documentation

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• CI/CD or build configuration change
• Refactoring (no functional changes)

Testing

• Tests pass locally (cd desktop && npm run test)
• Renderer tests pass locally (cd desktop/renderer && npm run test)
• Build succeeds (cd desktop && npm run build)
• Manual testing performed (describe below)

Validated the complete Windows build and installer. Confirmed the base installer does not contain rednote-publisher, while the packaged desktop contains an identical dormant agent-skill resource. Exercised the full Creative Muse workflow to produce and validate a sourced topic list, material kit, cover, six carousel cards, post copy, hashtags, sources, and upload checklist.

Local results:

• Desktop main-process tests: 818 passed
• Renderer tests: 262 passed
• Python installer tests: 106 passed
• Full build.ps1: passed

Checklist

• My code follows the coding guidelines of this project
• I have performed a self-review of my code
• I have commented my code where necessary
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or my feature works
• New and existing unit tests pass locally with my changes