integration: gs ss from integration submits all tip stacks

[ed-irl]

integration: gs ss from integration submits all tip stacks

'gs ss' is "submit the current stack", but the integration branch is
not part of any stack — it's the union of multiple. Running 'gs ss'
from there previously crashed with "branch not found in store"
because the lookup against the branch graph fails for untracked
branches.

When the current branch matches the configured integration name,
dispatch into an integration-aware path: collect the full stack
(upstack + downstack, trunk excluded) of each configured tip in
trunk-first topological order, dedup branches shared across tips,
hand the result to SubmitBatch, then push the integration branch
itself with its existing force-with-lease semantics.

This is broader than 'gs integration submit' (which only submits the
downstack of each tip); 'gs ss' is the "submit everything in this
stack" command, and from integration that means upstack too.

integration-stack-submit: Regenerate derived files

[ed-irl]

This change is part of the following stack:

• restack: Add Options parameter to high-level restack entry points #1307
  • feat: Add worktree commands with per-worktree trunks #1249
    • feat(worktree): Add worktree commands, per-worktree trunks, and worktree-aware filtering #1188
      • worktree: Add worktree commands, per-worktree trunks, and worktree-aware filtering #1165
        • feat: Add worktree commands, per-worktree trunks, and worktree filters #1172
          • worktree: Add worktree management commands, per-worktree trunks, and worktree-aware filtering #1173
            • integration: Wire auto-rebuild hook on restack commands #1174
              • integration: Auto-rebuild integration branch after restack #1175
                • integration: Auto-rebuild integration branch on restack #1176
                  • integration: Add AI-driven conflict resolution #1251
                  • integration: Move regeneration out of merge driver #1252
                  • integration: accept-incoming fallback after auto-resolve #1253
                  • integration: submit tip downstacks alongside the integration branch #1254
                  • integration: surface integration branch and tips in gs ll #1255
                  • integration: short-circuit gs branch checkout for the integration #1256
                  • integration: gs ss from integration submits all tip stacks #1257 ◀
                  • integration: tip clean prunes subsumed tips #1258
                  • integration: tip advance moves tips to upstack leaves #1259
                  • integration: rebuild fixes and reliability improvements #1260

_{Change managed by git-spice.}