fix(test:apps): inject boxlite_dev tag via GOFLAGS for apps Go tests (#579)

[G4614]

Set GOFLAGS=-tags=boxlite_dev on the make test:apps recipe so the apps' Go tests link the dev-built target/debug/libboxlite.a (via sdks/go/bridge_cgo_dev.go) instead of the prebuilt bundle absent on dev checkouts — fixes #579.

[G4614]

Caveat — the tag is injected only via make test:apps, not bare yarn nx test <project>

Line 309 sets GOFLAGS=-tags=boxlite_dev for the nx run-many it spawns, so it covers make test:apps (and CI, which runs through make). A standalone yarn nx test <project> in a shell without GOFLAGS does not get the tag. Consequences:

• The 8 pure-Go apps — the tag is a no-op, so they're unaffected.
• runner (the only app importing the cgo bridge), run standalone without the tag:
  • Normal dev checkout (no downloaded prebuilt bundle): loud link failure — the make test:apps fails in dev workflow: libboxlite.a not populated at default-bridge path #579 symptom. Safe; fix by running via make.
  • If a contributor has also run the setup downloader and pulled the prebuilt bundle into their checkout: it silently links the released sdks/go/libboxlite.a instead of their local target/debug build — tests go green but don't exercise local Rust changes.

Neither case affects CI. If standalone nx test ever becomes a common workflow, close the gap by switching the Go test targets to nx:run-commands with inline GOFLAGS (bakes the tag into the target config so it applies however the target is invoked) — not direnv/options.env (the latter is dropped by @nx-go/nx-go:test, which forwards only cwd to the spawned go).

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Test plan

• Tag selects the dev bridge (go list -f '{{.CgoFiles}}' in sdks/go): GOFLAGS=-tags=boxlite_dev → bridge_cgo_dev.go (in-repo sdks/c/include + target/debug/libboxlite.a); no tag → bridge_cgo_prebuilt.go (needs the absent downloaded bundle, i.e. make test:apps fails in dev workflow: libboxlite.a not populated at default-bridge path #579).
• Env reaches the Nx-spawned go test (unchanged @nx-go/nx-go:test executor): GOFLAGS=-zzz_bogus yarn nx test api-client-go → go: parsing $GOFLAGS: unknown flag -zzz_bogus; GOFLAGS=-tags=boxlite_dev yarn nx test api-client-go → Successfully ran target test.