docs(roadmap+milestones): mark A6.P1/A6.P2 shipped; update M1.5 demo

A6.P1 (cdb probe spike) + A6.P2 (analysis report) both SHIPPED this
session. Updated:

  docs/plans/2026-04-11-roadmap.md — M1.5 phase block now shows A6.P1
  + A6.P2 SHIPPED with commit refs; A6.P3 entry expanded with the
  Finding-2-first sequencing recommendation from A6.P2; A6.P4 entry
  notes the original "Holtburg Sewer end-to-end" acceptance walk is
  unreachable (sewer doesn't exist).

  docs/plans/2026-05-12-milestones.md — M1.5 demo scenario split into
  building/cellar half (achievable post-A6.P3) + dungeon half (blocked
  on issue #95 visibility blowup; promote to post-M1.5 if #95 isn't
  fixed in scope). Issue list updated: added #95 + indoor sling-out
  (new from scen4); marked stairs/2nd-floor/cellar as characterized by
  A6.P2 Finding 2 family.

  CLAUDE.md — Currently-working-toward block now points at A6.P3 as
  the active phase. A6.P1 + A6.P2 ship noted with the findings doc
  pointer. Demo-scenario note updated to reflect the sewer + #95
  reality. Issues-in-scope updated.

Also includes a 1-line trailing-prompt addition to scen3 + scen4
retail.log files (cdb wrote one more `0:000>` after the kill that
landed after the original capture commits).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/research/2026-05-21-a6-captures/scen3_inn_2nd_floor/retail.log

@@ -21335,3 +21335,4 @@ ntdll!NtTerminateProcess+0xc:
 7748949c c20800          ret     8
 0:000> 
 [BP4] find_collisions hit#10636 collide=Memory access error at '), dwo(poi(@esp+4)+0x174), dwo(@esp+8); .if (@$t0 >= 50000) { qd } .else { gc }'
+0:000> 

docs/research/2026-05-21-a6-captures/scen4_cottage_cellar/retail.log

@@ -22534,3 +22534,4 @@ ntdll!NtTerminateProcess+0xc:
 7748949c c20800          ret     8
 0:000> 
 [BP4] find_collisions hit#12596 collide=Memory access error at '), dwo(poi(@esp+4)+0x174), dwo(@esp+8); .if (@$t0 >= 50000) { qd } .else { gc }'
+0:000>