Add sequential single-item auction for multi-robot task

[vishwagw]

Reference issue

Closes #: 1460

What does this implement/fix?

Adds a Sequential Single-Item (SSI) auction for multi-robot task allocation under Mission Planning (Lagoudakis et al., RSS 2005; Koenig et al., AAAI 2006).

Each round, every robot bids on every unassigned target and the lowest bid wins; the target is inserted into the winner's route at its cheapest position. Two team objectives:

• MiniSum: bid = marginal cost → minimizes total distance
• MiniMax: bid = new route cost → minimizes the longest route (completion time)

Travel costs are A* path lengths reusing PathPlanning/AStar/a_star.py, so allocations respect obstacles. Only existing requirements are used.

Files:

• MissionPlanning/SequentialSingleItemAuction/sequential_single_item_auction.py: example with main() and show_animation
• tests/test_sequential_single_item_auction.py: 9 tests
• docs/modules/13_mission_planning/sequential_single_item_auction/sequential_single_item_auction_main.rst: problem, math, algorithm, results, comparison with related methods, autodoc links; added to the Mission Planning toctree

Results on the example map:

Objective	Total distance	Longest route	Targets per robot
MiniSum	136 m	114 m	0, 9, 1
MiniMax	195 m	76 m	1, 7, 2

Additional information

• Animation GIF PR:
• Tests include obstacle awareness (a target behind a wall goes to the robot with the shorter path, even though another robot is closer in a straight line) and the MiniSum/MiniMax trade-off.
• Locally on Python 3.13 with the pinned requirements: pytest tests -Werror → 165 passed, including the codestyle and mypy tests. mypy on the new module is also clean. MissionPlanning isn't in the mypy test's package list, so I ran it separately.
• Docs built with Sphinx with no warnings for the new page. I checked the rendered HTML: the page is reachable from Mission Planning, and the table and parameter sections render.

CheckList

• Did you add an unittest for your new example or defect fix?
• Did you add documents for your new example?
• All CIs are green?