docs(plans): record S09 enforcement step MRs, amend steps 11 and 13

What does this MR do?

Two things, both single-writer plan-file edits for the S09 enforcement plan:

1. Fills the Status table rows with their step MRs (rows 1, 4, 5, 6, 7, 8, 10, 12, and 14):

Row	Step MR
1	!1919 (merged)
4	!2008 (merged)
5	!1918 (merged)
6	!1954 (merged)
7	!2009 (merged)
8	!1960 (merged)
10	!2010 (merged)
12	!2016 (merged)
14	!1951 (merged)

2. Amends steps 11 and 13 with review-settled obligations from !2010 (merged)'s review threads: step 11's Depends on line carries the guard obligation so the two cannot merge out of order, step 11's acceptance counts the guard's rejections under their own denial_reason label, and step 13's parity test compares (route, method) to action rather than route shape alone.

Why a separate MR

Step MRs do not edit the plan file, the Status table included: parallel step MRs editing adjacent rows of the same table conflict whichever lands second, and on a merge train that blocks the merge outright. The plan file takes a single writer instead, so the pending rows and the step amendments are batch-recorded here. The title carries no step marker — that marker belongs to the step MRs alone.