Add docs deploy concurrency guard and Sienna aggregate refresh dispatch.

[kdayday]

Serialize main/tag docs deploys while allowing PR preview cancel; notify the Sienna site after successful non-PR docs publishes.

[github-actions]

Performance Results

Precompile Time

Main	This Branch	Delta
2.3 s	2.3 s	+0.2%

Execution Time

Cells show median (min–max) over 5 samples; delta compares medians.

Test	Main	This Branch	Delta
matpower_ACTIVSg2000_sys-Build Ybus	10.5 (10.3–13.2) ms	10.6 (10.3–11.4) ms	+1.7%
matpower_ACTIVSg2000_sys-Build PTDF	71.9 (70.9–73.5) ms	74.4 (72.7–74.8) ms	+3.5%
matpower_ACTIVSg2000_sys-Build LODF	151.5 (150.5–152.3) ms	153.8 (153.0–154.9) ms	+1.6%
matpower_ACTIVSg2000_sys-Build VirtualMODF	110.5 (110.2–111.4) ms	1.1 (1.1–1.1) s	+924.0%
matpower_ACTIVSg2000_sys-VirtualMODF Query 10 rows	0.6 (0.5–1.2) ms	0.6 (0.6–1.7) ms	+6.1%
matpower_ACTIVSg2000_sys-Radial network reduction	0.7 (0.7–0.9) ms	0.8 (0.8–1.1) ms	+16.1%
matpower_ACTIVSg2000_sys-Degree two network reduction	1.1 (0.9–1.4) ms	1.1 (1.0–1.9) ms	-2.4%
Base_Eastern_Interconnect_515GW-Build Ybus	589.6 (582.2–600.6) ms	531.7 (529.0–545.6) ms	-9.8%
Base_Eastern_Interconnect_515GW-Build VirtualPTDF	830.0 (813.4–854.5) ms	771.9 (768.9–781.7) ms	-7.0%
Base_Eastern_Interconnect_515GW-VirtualPTDF Query 10 rows	25.6 (25.4–27.1) ms	24.7 (24.2–27.6) ms	-3.5%
Base_Eastern_Interconnect_515GW-Build VirtualMODF	829.4 (819.2–846.7) ms	850.5 (847.7–857.9) ms	+2.5%
Base_Eastern_Interconnect_515GW-VirtualMODF Query 10 rows	32.2 (31.4–33.4) ms	30.5 (28.8–33.6) ms	-5.1%
Base_Eastern_Interconnect_515GW-Radial network reduction	40.8 (39.5–42.8) ms	40.1 (39.1–45.0) ms	-1.8%
Base_Eastern_Interconnect_515GW-Degree two network reduction	47.9 (47.1–48.4) ms	45.5 (44.2–53.8) ms	-5.1%

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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