Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@microagents-cli/src/main.rs`:
- Around line 140-156: The fork flow in main currently clones parent events and
returns the new session id, but it never persists the SessionFork marker event.
After the child session is created in the event replay loop, add a write for the
SessionFork event through storage so the lineage is recorded distinctly from a
normal resumed session. Use the existing session-writing path in main alongside
the SessionInit and other event handling to place this marker at the right point
in the fork process.
- Around line 163-169: The forked startup logic in main.rs is treating
`--session-id` as the only way to continue into the TUI after `fork_session`,
which makes plain `--fork <parent>` exit early unless an unrelated value is
passed. Update the `resolved_session_id` handling so the forked TUI path uses
`Some(new_sid)` when `args.fork` is present and no prompt is provided, and
reserve the early return only for an explicit clone-only mode if you add one.
Keep the fix centered on `fork_session`, `resolved_session_id`, and the
`args.prompt` / `args.session_id` branch.

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@microagents-cli/src/main.rs`:
- Around line 139-152: The history cloning in main.rs is copying inherited
SessionFork markers from the parent and then adding a new fork marker for the
child, which leaves the new session with two fork origins. Update the
parent_events replay loop so SessionFork events are skipped (or otherwise not
rewritten/persisted) while cloning history, and only append the new
child-to-parent fork marker once after the loop. Use the existing event handling
around cloned_event, SessionInit, and storage.update_session/create_session to
locate the change.
- Around line 49-51: The CLI options are ambiguous because `fork` currently
overrides `session_id` silently; update the argument definitions in `main.rs` so
`--fork` and `--session-id` cannot be used together. Add the conflict on the
`fork` field in the argument struct, using the existing `fork` and `session_id`
symbols, so the parser rejects the combination instead of choosing one
implicitly.

---

Nitpick comments:
In `@microagents-events/src/lib.rs`:
- Line 293: The AssistantResponseEvent serialization change only has coverage
for the tool_calls: None case, so add a test that exercises the non-null
tool_calls path and verifies the JSON-RPC wire shape. Update the
serialization/round-trip test around AssistantResponseEvent and
serialize_to_jsonrpc to include tool_calls as Some(vec![...]) so the generic
serde path stays locked down.