[Codex] 5.4: Update CLI remote submission for API-key flow

[taariq]

Parent: #28

Depends on: #42 (Task 5.1), #38 (Task 3.3), #39 (Task 3.4)

Task

Update init and sync commands to send project identifiers in JobSpec when using API-key flow + --seren.

Files to Modify

• src/commands/init.rs
• src/commands/sync.rs

What to Change

When building JobSpec for remote submission:

• If using API-key flow (has TargetState), send target_project_id, target_branch_id, target_databases, seren_api_key
• If using traditional mode, send target_url as before

See docs/plans/api-key-flow-implementation.md Task 5.4 for full code.

How to Test

export SEREN_API_KEY=your_key
# Run init with remote execution
cargo run -- init --source "postgresql://localhost/test" --seren
# Should show interactive picker, then submit job with project identifiers

Commit Message

feat(init): Send project identifiers for remote API-key flow

[taariq]

Implemented Task 5.4 by updating the remote init/sync job submission to send project identifiers whenever an API-key flow was used:

• Added a SerenTargetMode helper and extended init_remote/resolve_target_for_sync to differentiate between explicit --target URLs and saved Seren selections.
• When running with an API key, the CLI now fills project_id, branch_id, target_databases, and seren_api_key in the JobSpec so the remote orchestrator can fetch credentials itself. It falls back to legacy target_url when no Seren metadata is available.
• Verified with cargo build.