Ticket 059: Deliberately Infeasible Demo Mission

Goal

Add one example mission that produces INFEASIBLE output — a route that fails a real check — and a short README note explaining what failed and what you would change to fix it. This requires no code changes.

Motivation

Every current example passes. A new user who runs all provided examples sees a tool that always says yes. The value of bvlos-sim is that it catches problems a spreadsheet would not catch. Without a failing example, the tool looks like a calculator that outputs green, not a validator that can output red.

Operators trust tools that demonstrate failure modes, not tools that only show passes. An infeasible example with a clear explanation — "this mission fails because the route crosses the restricted zone at wp2; shift the waypoint 500 m north to clear it" — is the moment a new user understands why the tool exists.

Scope

Two new files, no code changes:

File	Contents
examples/real_world/alpine_infeasible.yaml	Mission that fails one or more checks
Update examples/real_world/README.md	Section showing the failure output and fix

The failure should be real and meaningful — not a contrived energy budget exhausted by a 10,000 km route. Candidate failure modes:

1. Geofence conflict — route leg intersects a forbidden zone in the committed geofences.geojson when that asset contains a relevant airspace polygon; fallback: use the existing synthetic data/geofences/demo.geojson.
2. Insufficient reserve for terrain — battery too small for the elevation gain on the alpine route, ending with reserve_at_landing_wh < threshold.
3. Landing-zone unreachable — min_distance_to_landing_zone_m constraint tighter than any available landing zone; useful if the committed geofence asset is empty for the route area.

Option 2 (energy/reserve failure) is self-contained and does not depend on a non-empty geofence asset. Use a reduced battery_capacity_wh in a local vehicle override or a second vehicle YAML (e.g. alpine_small_battery.yaml) to make the failure legible without editing the real quadplane profile.

README note format

After the passing estimate command, add:

## What a failing mission looks like

This mission uses a smaller battery and fails the reserve check:

  uv run bvlos-sim estimate \
    examples/real_world/alpine_infeasible.yaml \
    examples/real_world/quadplane_small_battery.yaml \
    --format summary

Output:
  INFEASIBLE [ENERGY_RESERVE]   reserve −12.4 %   flight 8m 22s

The reserve drops below the 25 % threshold because the battery (300 Wh) is
too small for the 450 m terrain climb on the wp_ridge leg at alpine cruise
power. Fix: increase battery_capacity_wh to at least 520 Wh, or reduce the
altitude gain by lowering the waypoint altitude or re-routing around the ridge.

Acceptance Criteria

1. uv run bvlos-sim estimate examples/real_world/alpine_infeasible.yaml examples/real_world/quadplane_small_battery.yaml --format summary exits non-zero and prints INFEASIBLE.
2. The failure reason is real (not a nonsensical constraint) and the README explains both what failed and how to fix it.
3. All existing tests continue to pass.

Out of Scope

• Geofence-based failure unless the committed or refreshed geofence asset contains a forbidden zone in the route area.
• Any code changes to the estimator or CLI.