fix(cli): preserve agent profile fields when setting policy

[xianjianlf2]

Closes #4490

What changed

• Read the current kind:10100 agent profile before updating the channel-add policy.
• Preserve existing profile fields such as name and respond_to while replacing channel_add_policy.
• Return a clear error for malformed or non-object profile content.
• Add a regression test for field preservation.

Validation

• cargo fmt --all
• cargo test -p buzz-cli set_add_policy

[Chessing234]

looks right — read-merge-write on kind:10100 so set-add-policy keeps name/respond_to. one nit: if prior content is valid json but not an object, you hard-error; maybe worth a short note in the pr body so ops aren't surprised.

[xianjianlf2]

Updated this branch with current main and resolved the channels.rs merge conflict while preserving the kind:10100 profile carry-forward behavior.\n\nValidation run locally:\n- cargo fmt --check\n- cargo test -p buzz-cli channels\n\nAlso noting the maintainer nit: the current behavior intentionally errors if an existing kind:10100 profile is valid JSON but not an object, because there is no safe object field to preserve/update in that case.

[xianjianlf2]

Follow-up: amended the merge commit with the required DCO signoff and force-pushed with --force-with-lease. DCO is now passing on head f503f68.

[wolfyy970]

This fixes the current field-clobbering bug cleanly. The command now preserves the existing profile object, changes only channel_add_policy and fails closed on malformed content.

I checked exact head f503f68. All five focused tests, strict buzz-cli Clippy, formatting and the diff check pass.

This is worth landing as the narrow fix for #4490. It does not remove the concurrent two-writer race discussed on #5546, so that review still stands.

[xianjianlf2]

Resolved conflicts against upstream main.

Validation:

• cargo test -p buzz-cli commands::channels::tests (60 passed)
• cargo fmt --check
• git diff --check

Current head: 27dda20

[github-actions]

🔐 Codex Security Review

Status: review required for the current range.

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[xianjianlf2]

Amended the merge commit with DCO signoff.

Current head: 5cf7608