Adds a read-only Status RPC to the gateway that returns the current
customer-friendly status of a previously submitted request, reconciled
from the append-only request log via
core/request.GetCurrentStateFromRequestLog. Status is a free-form string
(statuses can be added without breaking clients); unknown sqids map to a
typed RequestNotFoundError (user error) and empty sqids to ErrInvalidRequest.

Named "Status" to match the gateway's short RPC naming (Ping, Land, Status).

Changes:
- gateway/proto/gateway.proto: Status RPC, StatusRequest/StatusResponse, and
  RequestNotFoundError messages (regenerated protopb)
- gateway/controller/status.go: StatusController + tests
- example/server/gateway/main.go: wire controller (reuses existing RequestLogStore)

Validation:
- Unit tests: bazel test //gateway/controller:controller_test  (PASS)
- Integration (local stack): make local-gateway-start
  PORT=$(docker port submitqueue-gateway-service-1 8080 | head -1 | cut -d: -f2)

  # method is registered
  grpcurl -plaintext localhost:$PORT list uber.submitqueue.gateway.SubmitQueueGateway
    -> Land, Ping, Status

  # seed a request
  grpcurl -plaintext -d '{"queue":"test-queue","change":{"uris":["github:///pull/123/c3a4d5e6f7890123456789abcdef0123456789ab"]}}' \
    localhost:$PORT uber.submitqueue.gateway.SubmitQueueGateway/Land
    -> { "sqid": "test-queue/1" }

  # happy path
  grpcurl -plaintext -d '{"sqid":"test-queue/1"}' \
    localhost:$PORT uber.submitqueue.gateway.SubmitQueueGateway/Status
    -> { "status": "accepted" }

  # unknown sqid
  grpcurl -plaintext -d '{"sqid":"test-queue/999"}' \
    localhost:$PORT uber.submitqueue.gateway.SubmitQueueGateway/Status
    -> ERROR: request not found for sqid "test-queue/999"

  # empty sqid
  grpcurl -plaintext -d '{"sqid":""}' \
    localhost:$PORT uber.submitqueue.gateway.SubmitQueueGateway/Status
    -> ERROR: StatusController requires the request to have a sqid specified: invalid request

Co-authored-by: Cursor <cursoragent@cursor.com>

…for go-code compatibility (uber#293)

<!-- Provide a summary in the Title above. Example: "Feature: add user
authentication" -->

## Why?
We want the smoothest DX for consuming the OSS submitqueue repo in
go-code. Today go-code's `go_repository` uses `build_file_generation =
"on"`, so its Gazelle regenerates BUILD files for the vendored repo.
This causes conflicts and mismatches, and every version bump risks new
patching.

The root issue is that OSS carries proto types twice: as checked-in
`.pb.go` in `protopb/`, and as Bazel-generated code via
`go_proto_library` in `proto/`. Removing the Bazel proto rules in favor
of the checked-in `.pb.go` fixes several things at once:

- Eliminates duplicate proto definitions. The two generation paths share
the same importpath, which caused the duplicate-importpath ambiguity and
forced the `gazelle:resolve` workarounds. Collapsing to a single source
removes that whole class of conflict.
- Serves non-Bazel consumers. The Bazel-generated code only exists
inside a Bazel build graph. Anyone consuming submitqueue via plain `go
build/go get` (including OSS users) can only use the checked-in .pb.go,
so that path must work regardless. The Bazel proto rules are a redundant
second path that serves no one the checked-in files don't already serve.

## What?
Disable Gazelle proto rule generation and remove all proto compilation
rules, relying solely on checked-in `.pb.go` files.

- Add `# gazelle:proto disable_global` to prevent Gazelle from
regenerating proto rules on future make gazelle runs
- Remove the `gazelle:resolve directives` that are no longer needed
- Remove `proto_library`, `go_proto_library`, and alias `go_library`
rules
- Keep `exports_files` for `make proto` codegen
(`tool/proto/BUILD.bazel`)

## Test Plan
- `make build` - pass
- `make test` - 65/65 unit tests pass (integration/e2e tests fail due to
Docker dependency, pre-existing)
- `bazel build //tool/proto:generated` - proto codegen still works
- `make gazelle` - zero warnings, no duplicate-importpath ambiguity
- Validated in go-code with `--override_repository` pointing at this
branch: all 71 targets build, all 20 tests pass across stovepipe,
submitqueue/gateway, and submitqueue/orchestrator

## Issue
<!-- 
Link the issue here. 
- Use 'Closes uber#123' if this is the final fix. 
- Use 'Part of uber#123' or just 'uber#123' if the feature is still in progress.
-->

---------

Co-authored-by: chenghan.ying <chenghan.ying@uber.com>

Adopt go_default_library naming convention for Bazel targets 

## Why?
The internal go-code monorepo consumes this repo via Bazel with
`build_file_generation = "off"` - it uses the checked-in `BUILD.bazel`
files **directly** instead of regenerating them. go-code's gazelle
enforces the`go_default_library` naming convention for all external
repos globally (`# gazelle:go_naming_convention_external
go_default_library`), so every dependency label it writes points at
`:go_default_library`. For go-code to reference this repo's targets
without per-import fixups, our targets must be reachable as
`:go_default_library`.

This complements the proto-disable change
(#293): together they let
go-code build this repo out of the box on Bazel 8.5.1 (which removed
`native.java_proto_library`, breaking `proto_library`).

## What?
- Add `# gazelle:go_naming_convention go_default_library` to the root
`BUILD.bazel` and regenerate target names via gazelle:
libraries/binaries ->`go_default_library`, tests -> `go_default_test`;
external refs normalize to `:go_default_library`.
- Manually migrate hand-authored, custom-named test targets that gazelle
cannot rename across a convention change:
- 9 integration/e2e `go_test` targets - `go_default_test` (`data`/`tags`
preserved once the name matches the convention),
- remove the redundant `platform/consumer:consumer_test` (gazelle now
emits `go_default_test` for that package),
  - point the `Makefile` integration-test targets at `:go_default_test`.
- Drop redundant `# keep`-pinned short-name `protopb` deps - under the
new convention the `:go_default_library` equivalents are emitted beside
them, so the short-name `:protopb` labels are dangling.

## Test Plan
- `make gazelle` - clean and idempotent (no duplicate-rule errors).
- `make build` -  223 targets built.
- `make test` -  65/65 unit tests pass.
- Verified downstream consumption from go-code with
`build_file_generation="off"`
  by overriding the module at this branch:
  bazel test //src/.../submitqueue/{gateway,orchestrator,stovepipe}/...
--override_repository=com_github_uber_submitqueue=/path/to/submitqueue
  -  71 targets build, 20/20 consumer tests pass.


## Issue
<!-- 
Link the issue here. 
- Use 'Closes #123' if this is the final fix. 
- Use 'Part of #123' or just '#123' if the feature is still in progress.
-->

Co-authored-by: chenghan.ying <chenghan.ying@uber.com>