docs(v2.0.0-alpha.3): inline plot injection across the entire doc tree

Add scripts/inject_doc_plots.py that scans every .md and .rst page under
docs/source/, executes each Python code-block in an isolated namespace
with a non-interactive matplotlib backend, captures every figure
produced, and inserts an inline image directive immediately after the
code-block.  Markers AUTO-PLOT-BEGIN/END make the injection idempotent
on re-runs.  Blocks that fail to execute or produce no figure are left
untouched.

Add a transparent __getattr__ fallback in python/optimizr/__init__.py
that forwards any unresolved top-level attribute to the compiled _core
extension.  This lets all v1.x and v2.0 doc samples that use
'from optimizr import X' (estimate_ou_params_py, linear_bsde_constant_coeffs,
mmd_gaussian, ...) execute as written.

Augment the OU Parameter Estimation example
(docs/source/algorithms/optimal_control.md) with a two-panel
visualization (simulated path plus empirical/theoretical autocorrelation).

Net effect: 14 doc pages now display matplotlib plots inline directly
under the code that produced them -- including the OU page, point
processes, Grid Search, HMM, MCMC, plus the 8 v2.0 RST pages.

docs/source/api/point_processes.md

@@ -207,6 +207,10 @@ plt.suptitle("Fractional Brownian Motion: Three Regimes")
 plt.tight_layout()
 plt.show()
 ```
+<!-- AUTO-PLOT-BEGIN -->
+![Generated plot](../_static/auto/api__point_processes/block_04_fig_01.png)
+<!-- AUTO-PLOT-END -->
+
 
 ---
 
@@ -401,6 +405,10 @@ plt.title('Scaling Function (Theorem 3.1)')
 plt.grid(True, alpha=0.3)
 plt.show()
 ```
+<!-- AUTO-PLOT-BEGIN -->
+![Generated plot](../_static/auto/api__point_processes/block_09_fig_01.png)
+<!-- AUTO-PLOT-END -->
+
 
 ---