* MNT: final fixes before next release

Documentation, CHANGELOG and test polish ahead of the next release
(v1.13.0), covering PRs merged since v1.12.0.

CHANGELOG
- Add missing entries: Individual Fins (#818), AIGFS/HRRR forecast
  models (#951), duplicate-controller fix (#949), Valkyrie flight
  example (#967).
- Hygiene: de-duplicate #958/#966, move #974 to Fixed and #1041 to
  Removed only, drop the already-released #914 duplicate, and point the
  logging (#973) and ND-interp (#969) entries at their PRs.
- Backfill #940/#941/#944 (shipped in v1.12.0 code but never logged)
  under the [v1.12.0] section.

Docs
- New exceptions reference page (rocketpy.exceptions) wired into the
  reference index; note UnstableRocketWarning in the rocket stability
  docs (#970).
- tanks.rst: switch examples to radius_function= and add a deprecation
  note (#957).
- forecast.rst: fix the HRRR example (missing code directive + stray
  sentence) (#951).
- airbrakes.rst: document discrete vs continuous controllers
  (sampling_rate=None) (#946).
- rocket_usage.rst: note that Parachute is now an abstract base;
  instantiate HemisphericalParachute (#958).

Tests
- New regression tests: 3D ND-interp NaN outside convex hull (#969),
  abstract Parachute cannot be instantiated (#958), Monte Carlo
  convergence stopping (#922), EnvironmentAnalysis surviving wind API
  (#1041), radial-burn grain geometry over time (#944), RingClusterMotor
  full flight (#924), discrete controller invoked once per node (#949),
  acceleration-based parachute trigger deploys (#911).
- Backfill regression tests for ThrustCurve API timeouts (#940) and
  power_off/on_drag Function objects + _input attributes (#941).


* make format