gsd-insert-phase by @shoootyou

<objective> Insert a decimal phase for urgent work discovered mid-milestone that must be completed between existing integer phases.

Uses decimal numbering (72.1, 72.2, etc.) to preserve the logical sequence of planned phases while accommodating urgent insertions.

Purpose: Handle urgent work discovered during execution without renumbering entire roadmap. </objective>

<execution_context> @{{PLATFORM_ROOT}}/get-shit-done/workflows/insert-phase.md </execution_context>

<context> Arguments: $ARGUMENTS (format: <after-phase-number> <description>)

Roadmap and state are resolved in-workflow via init phase-op and targeted tool calls. </context>

<process> Execute the insert-phase workflow from @{{PLATFORM_ROOT}}/get-shit-done/workflows/insert-phase.md end-to-end. Preserve all validation gates (argument parsing, phase verification, decimal calculation, roadmap updates). </process>