Remove stale bundled-launcher references from test/unit/session-start.bats

[ivklgn]

Problem

The bundled CLI launcher was removed in v0.4.0, but test/unit/session-start.bats still carries a test built around it:

267: @test "survives when launcher cannot resolve CLI (no PATH, no cache, no network)" {
268:   # Initialized project + restricted PATH + ARCHCORE_SKIP_DOWNLOAD=1:
269:   # launcher exits 1, but session-start wraps with '|| true' and still succeeds.
274:   run sh -c "PATH='/usr/bin:/bin' ARCHCORE_SKIP_DOWNLOAD=1 printf '%s' '{}' | '${PLUGIN_ROOT}/bin/session-start'"

ARCHCORE_SKIP_DOWNLOAD is read by no shipped script — grep -rn ARCHCORE_SKIP_DOWNLOAD plugins/ returns nothing — so it is a dead no-op, and the title and comment describe a launcher that no longer exists. The test still passes, which is exactly why nobody notices.

Expected result

The test drops the removed ARCHCORE_SKIP_DOWNLOAD variable and is reworded to the current model: the CLI is simply absent from PATH, bin/session-start wraps archcore with || true, and the hook still succeeds.

Impact

Removes a misleading, dead test path — small hygiene fix completing the v0.4.0 launcher removal, and a friendly first contribution.

Proposed approach

• Rewrite the test case: drop the env var, reword the title and comment to "CLI absent from PATH".

Acceptance criteria

• No reference to ARCHCORE_SKIP_DOWNLOAD or "launcher" remains in test/unit/session-start.bats; make test still passes.

References

Design rationale: .archcore/plugin/remove-bundled-launcher-global-cli.idea.md (revert step 7). Code: test/unit/session-start.bats:267-274.