v0.4.0

• ci(landing): redeploy landing after a successful release
• chore: gitignore playwright e2e artifacts
• docs: document density token engine + shape rule
• test(density): enforce zero literals in CI
• test(density): e2e proving density drives spacing/height + shapes stay square
• refactor(density): tokens in remaining modals
• refactor(density): tokens in settings-modal
• refactor(density): tokens in workspace
• refactor(density): tokens in dev-tools
• refactor(density): tokens in backlog
• docs(density): add SHAPE RULE to sweep procedure
• fix(density): preserve circle/square shapes + fix shell grid gap
• refactor(density): tokens in right-panel
• refactor(density): tokens in sidebar
• @ feat(backlog): snake_case ticket tags + factorized top-bar action pill
• refactor(density): tokens in overview
• refactor(density): tokens in notifications
• refactor(density): tokens in shared components
• refactor(density): tokens in top-bar
• refactor(density): tokens in tweaks panel
• @ feat(agents): forward selected model + reasoning effort to the CLI
• docs(plans): density-driven CSS variables implementation plan
• docs(specs): density-driven CSS variables design
• refactor(density): tokens in status-bar
• fix(density): extend spacing scale (sp-10/sp-11); margins use sp-*, not ctl-h
• refactor(density): tokens in shell/context-menu/loading
• refactor(density): tokens in styles.css atoms
• feat(density): literal scanner + unit tests
• test(density): assert token engine structure
• docs(density): resolve --hair collision (color, not width token)
• feat(density): add density-factor token engine (spacing/height/type scale)
• docs(plans): density-driven CSS variables implementation plan
• docs(specs): density-driven CSS variables design