[CLI] Add --output flag to inv list for machine-readable output

[OmarAshour02]

Summary

Closes #3872

• Adds a global --output flag (human | table | json | jsonl) to restate inv list
• human is unchanged (existing pretty output with colors and icons)
• table emits plain columns suitable for awk/grep pipelines
• json / jsonl emit serializable Invocation data, enabling patterns like:

restate inv list --status backing-off --output jsonl | jq -r .id | xargs restate inv cancel

The flag is wired as a global option in cli-util (--output in UiOpts), so extending it to other list/describe commands in follow-up PRs is straightforward.

Changes

• crates/cli-util/src/opts.rs — new OutputFormat enum, added to UiOpts as a global flag
• crates/cli-util/src/context.rs — output_format() accessor
• crates/cli-util/src/lib.rs — re-export OutputFormat
• cli/src/clients/datafusion_helpers/mod.rs — Serialize on Invocation, SerializeDisplay on InvocationState, SerializeAs impl for DatafusionServiceType
• cli/src/commands/invocations/list.rs — format dispatch

Examples

--output table

   ID                   TARGET                STATUS     DEPLOYMENT         CREATED AT
   inv_13O9pdhD...sgh   Counter/test-key/add  completed  dp_158Betj...1L    2026-05-15T21:32:31+03:00

--output jsonl

  {"id":"inv_13O9pdhDeY4C75cnaN9rciSH7el4OT2sgh","target":"Counter/test-k
  ey/add","target_service_ty":"VirtualObject","created_at":"2026-05-15T21
  :32:31.869+03:00","status":"completed",...}
  {"id":"inv_1l3Hc716hrBy1SqoVNamSSRiWi7bWkykTL","target":"Counter/alice/
  get","target_service_ty":"VirtualObject","created_at":"2026-05-15T19:23
  :29.617+03:00","status":"completed",...}

Test plan

• restate inv list --output human — same output as before
• restate inv list --output table — plain tabular output, no colors
• restate inv list --output json — valid JSON array
• restate inv list --output jsonl | jq -r .id — extracts IDs correctly

[claude]

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