feat: make optimal-P estimation default (no --estimate-optimal-p flag required)

[nerdCopter]

Context

Optimal P estimation is currently opt-in via --estimate-optimal-p. The flag was added conservatively while the feature was experimental, but the analysis requires only setpoint[3] (throttle channel) which is present in nearly all Betaflight/EmuFlight logs.

Proposal

Gate the feature on setpoint[3] availability rather than an explicit flag. If throttle data is present, run the torque-inertia profiler and optimal-P analysis automatically alongside the existing step-response output.

Considerations

• The --estimate-optimal-p flag would be removed (or silently accepted and ignored for backwards compatibility).
• This work is naturally coupled with the double-parse fix — see perf/feat: eliminate double-parse and make optimal-P estimation default (no flag required) #146 — since removing the flag means profiling always runs, making the unified single-parse path even more important.
• The feature label Optimal P (Experimental, log-derived) already signals experimental status to users.

References

• Feature introduced in feat: Physics-based optimal P estimation with prop-size-aware recommendations #132; carried into feat: torque-inertia profiler & optimal P estimation (squash-rebase onto #143) #145
• Discussed during feat: torque-inertia profiler & optimal P estimation (squash-rebase onto #143) #145 development; deferred post-merge

[nerdCopter]

Consolidated into #146 — these two items are tightly coupled and should be resolved together.