…when the actor is unknown, stop failing silently

Three changes to the BrowserStack re-run delivery path.

1. BROWSERSTACK_BUILD_RUN_IDENTIFIER has been dropped since 2026-05-07.
The rebuild/details response carries three variables; the APS-19076 allowlist
(8ade0a3) listed only two plus BUILD_NAME, so the identifier is filtered out and
only a core.warning marks it. Verified against the live API. The SDKs send it as
build_run_identifier in the build-start payload, which files a re-run as an
attempt of its parent build rather than an unrelated build. PR #85's own body
predicted this: "If the rerun API legitimately sets additional names in
production, the list will need to grow."

2. An unreported GITHUB_TRIGGERING_ACTOR no longer aborts delivery.
That variable comes from the runner binary, so a self-hosted runner can simply
not set it. The actor check is only a cheap pre-filter — rebuild/details is the
authority and returns no variables when BrowserStack did not trigger the re-run.
Bailing on an absent actor turned a working re-run into a full-suite run on an
otherwise correctly configured workflow. We now warn and ask the API instead.

3. Every remaining delivery failure names itself.
With github-token at its 'none' default the job log was byte-identical to a
healthy run, and the CLI then runs the full spec set because
BROWSERSTACK_RERUN_TESTS is absent — so "all my tests ran again" was
undiagnosable. checkIfBStackReRun now names the missing input, a human-triggered
re-run says so, and an API failure is a warning rather than info. Attempt 1 stays
silent: an ordinary run is not a degraded re-run.

Verified end-to-end through the built dist into the real CLI across all eight
delivery states, and reproduced against a real reported failure: the build ran
11 sessions, the targeted spec folder holds 11 specs, and the real CLI dispatches
11 with the list absent and 3 with it present.

47 tests passing (4 new), eslint clean, dist rebuilt with ncc (reproducible).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

…identifier-and-diagnostics

[SDK-7461] fix(setup-env): deliver BUILD_RUN_IDENTIFIER, ask the API when the triggering actor is unknown, stop failing re-run delivery silently