Prevent restock reserves from blocking depot returns

[adrunkhuman]

• Separate depot travel from later shopping costs. Bot One had 198 gp and a 50 gp return fare, but an 820 gp restock reserve blocked patrol and left him retrying in place. Depot-bound travel now requires only its fare; outbound travel protects the return fare, and supplier travel retains the restock reserve.
• Reuse return-route evidence across complete, same-floor walks without modeled danger. Added danger, transitions, route failures, and changed route inputs require revalidation. A changed return fare also rechecks the complete outbound fare before movement starts.
• Count rejected patrol preflights toward bounded recovery. Keep hunt-exit safety separate from payment policy so ordinary depot returns retain their existing risk fallback.
• Add deterministic coverage for fare budgets, return-route invalidation, and repeated rejection. Update the playerbot capability documentation.

[adrunkhuman]

Validation limits: the isolated PR snapshot passes the C++ contracts. Runtime checks used the local worktree, which also contains separate, uncommitted equipment/readiness changes excluded from this PR. Ten navigation/hunt scenarios passed; the base corpse scenario passed on rerun. The restored level-17 bot selected a depot and resumed movement.

The gameplay suite is not fully green: corpse_detour expects the removed hostile_detour event; corpse_inaccessible expects 20 seconds while the existing six-failure bound ends work earlier; depot_risk_fallback selects a safe route instead of emitting the expected fallback event. Those contracts are unchanged here.

[adrunkhuman]

Fixed the stale gameplay assertions in 7bf5e1b. Corpse detour now checks safe routing and successful loot instead of the removed event; inaccessible-corpse recovery checks the six-failure bound; depot routing checks safe-route precedence rather than requiring a risky fallback. Deterministic fallback-policy checks remain.

All three scenarios passed against an isolated snapshot of this PR plus these test fixes, excluding the unrelated equipment/readiness worktree changes. Navigation assertion regressions also passed. This resolves the three failures and the isolation gap for those scenarios reported above; the full gameplay suite was not rerun.