Fix: DO-0 track frontend assets and build freshness

[krzysztof-causalens]

Motivation and Context

Fifth slice of #623, stacked on #692. Static assets must update during development, and production artifacts must be detected as stale when their inputs change, including inherited configuration and sibling workspace sources. Interrupted publication keeps recoverable builds.

Implementation Description

The dev runner routes registered static changes through project revalidation, gives configuration changes precedence and reports collisions with Vite-emitted files. Static responses use mrmime for MIME lookup.

Build markers record workspace source inventories, effective TypeScript configuration reads, Vite configuration imports, dependency settings and patches, and declared plugin inputs. Env files are runtime configuration and never make a build stale. Python startup parses the marker and compares recorded inputs, including partial workspace checkouts, without invoking JavaScript tools. A later build validates abandoned staging and backup markers before recovering or cleaning them.

Plugins declare additional files, directories and environment names through dara() options; undeclared reads are outside the freshness guarantee. The static assets guide documents static/, add_static_folder, live updates, collisions and production deployment.

Any new dependencies Introduced

mrmime for filename-to-MIME lookup.

How Has This Been Tested?

• Full repository build, Python and JavaScript suites, lint and format checks. Regressions cover source additions and deletions, partial checkouts, asset target changes, optional configs, TypeScript inheritance, patches, symlink inventories, static collisions and interrupted publication.
• The demo app's marker rejects source edits, added files and changed static targets. Headless Chrome rendered Bokeh and Plotly in development, production and an artifact-only copy with an empty PATH; a new static file appeared live and a namespace collision blocked and then restored the frontend.

PR Checklist:

• I have implemented all requirements? (see JIRA, project documentation).
• I am not affecting someone else's work, If I am, they are included as a reviewer.
• I have added relevant tests (unit, integration or regression).
• I have added comments to all the bits that are hard to follow.
• I have added/updated Documentation.
• I have updated the appropriate changelog with a line for my changes.