Add Zenoh raw MAVLink driver

[joaoantoniocardoso]

Summary

• Extract MAVLink JSON zenoh driver into src/lib/drivers/zenoh/json.rs
• Share zenoh session via singleton in zenoh/mod.rs
• Add ZenohRaw driver for raw MAVLink frame pub/sub over zenoh topics
• Add parallel-safe integration test helpers, cargo-nextest, and zenoh integration tests

Topic layout

Driver	Subscribe	Publish
Zenoh (JSON)	mavlink/in	mavlink/out
ZenohRaw	mavlink_raw/in	mavlink_raw/out

Follow-up

CI improvements (sccache, cross, shared frontend) are stacked in joaoantoniocardoso#1 — 3 commits on top of this branch. Open upstream CI PR after this merges.

Test plan

• CI green on 4746cfe: run 27261818195
• cargo nextest run (integration tests process-isolated)
• Confirm zenoh:// / zenohraw:// URL host/port intentionally ignored (session from --zenoh-config-file / defaults)

[joaoantoniocardoso]

Split from former #216 for review:

• This PR (Add Zenoh raw MAVLink driver #217) — Zenoh raw driver + test infra (12 commits)
• CI follow-up — 4 commits stacked on this branch: joaoantoniocardoso/mavlink-server#1 (fork PR; will retarget to upstream master after this merges)

[joaoantoniocardoso]

Fixed CI failure in 11a4ea8:

• Cause: parallel-safe integration tests (no `#[ignore]`) were still run via `cargo test`, which executes all tests in one process → driver UUID collisions.
• Fix: switch test job to `cargo nextest run` (process-per-test isolation). Also removed stray `println!` in `ZenohRaw::create_endpoint_from_url`.

[joaoantoniocardoso]

#217 CI is green on `11a4ea8`.

Stacked CI branch rebased onto this commit:

• Fork: `improve_ci` @ `e6346ff` → fork PR Improve CI caching and cross Linux builds joaoantoniocardoso/mavlink-server#1
• After merge here, open upstream CI PR targeting `master`

[joaoantoniocardoso]

Review notes (ZenohRaw / topic layout)

Topics

Driver	Subscribe (input)	Publish (output)
Zenoh (JSON)	mavlink/in	mavlink/out
ZenohRaw	mavlink_raw/in	mavlink_raw/out

Loopback prevention uses origin tag "zenohraw" on the raw path (JSON driver uses its own origin).

Session

• Shared singleton via OnceCell + watch channel; reconnect loop with 1s backoff.
• Default client connects to tcp/127.0.0.1:7447 unless --zenoh-config-file is set.

Endpoint URL

• zenoh:// / zenohraw:// host/port are parsed but not passed into the driver (session comes from global config). Worth confirming that is intentional for multi-router setups.

Cleanup in 4746cfe

• Removed stray println! from Zenoh JSON create_endpoint_from_url (same as raw driver fix in 11a4ea8).

[joaoantoniocardoso]

CI green on 4746cfe (includes json println cleanup): https://github.com/bluerobotics/mavlink-server/actions/runs/27261818195

[patrickelectric]