chore: update Bamboo provider endpoint retirement pointer

[bigduu]

Summary

• advance the Bamboo submodule pointer to the merged provider endpoint-retirement change
• carry Bamboo Issue #847 / PR #848 into the Zenith aggregate
• leave every other submodule pointer and root file unchanged

Submodule Updates

Submodule	Old SHA	New SHA	Rationale
bamboo	0256a3690fd64345cc18087d34e4002a33ec673c	f3b84b109e97099497bc397a45f6b2609eaa487b	Retire the legacy provider settings HTTP routes after the canonical provider-settings and Lotus cutover shipped (bigduu/Bamboo-agent#847, bigduu/Bamboo-agent#848).

Verification

• verified the new SHA is the live Bamboo dev merge commit for PR #848
• verified the old gitlink is an ancestor of the new SHA
• git diff-tree --check HEAD^ HEAD
• recursive raw diff contains exactly one 160000 gitlink update for bamboo

Screenshots

Not applicable; submodule pointer-only change.

[bigduu]

Agent review: APPROVE for exact head a46cb5695c6c3a656852ef9663267377e98c6126.

No P0, P1, or P2 findings.

Verified:

• the only root-tree change is the bamboo mode-160000 gitlink from 0256a3690fd64345cc18087d34e4002a33ec673c to f3b84b109e97099497bc397a45f6b2609eaa487b; every other blob/tree/gitlink is unchanged;
• the new SHA is Bamboo PR #848's merge commit and current dev; its first parent is the old pin, so this is a strict forward update;
• the PR body contains an exact ## Submodule Updates table and accurate #847/#848 rationale;
• both Submodule Guard checks pass on this exact head;
• the PR is MERGEABLE/CLEAN with no requested changes or review threads.

Verdict: approved. Reverify live head/base/checks/threads after changing Draft to Ready, then merge with expected-head protection.