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 contains a test titled "survives when launcher cannot resolve CLI (no PATH, no cache, no network)" whose comment and command reference ARCHCORE_SKIP_DOWNLOAD=1 (lines ~19-26). No shipped bin/ script reads that variable anymore, so it is a dead no-op and the test's title/intent are misleading (it still passes).

Expected result

The test drops the removed ARCHCORE_SKIP_DOWNLOAD variable and is reworded to reflect the current model: the CLI is simply absent from PATH, 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/comment to "CLI absent from PATH".

Acceptance criteria

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

References

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