Abort modes and feasibility recomputed live

**Abort modes** are pre-planned contingency burns: deorbit, free-return, abort-to-orbit, abort-to-rendezvous. Each one has a Δv requirement specific to your current mission state.

Abort Modes tab shows:
- Mode name + purpose
- Required Δv (mission-state-dependent — recomputed every time tanks change)
- Required engine(s)
- Window (when it's available)
- **Feasible?** — green/yellow/red. Green = you have enough propellant + working engine to execute it right now. Red = you cannot.

After every executed burn, abort feasibility is recomputed. If a planned mid-mission burn would push a critical abort from green to red, the planner shows a warning at approval time ("this burn makes free-return infeasible after T+05:14:00").

Wally tool `propulsion_abortFeasibility` returns the current feasibility table — useful in real-time ops when deciding whether to commit to a discretionary maneuver.

This is the live-recompute that catches the class of errors where a perfectly nominal burn drains reserves to the point that a later contingency is no longer possible.