Fix red develop 3f9866b299c8

The merge lane found `develop` red at `3f9866b299c83f85849826ca2638c1b7bdf98686` on its own: no queued PR merges until it is fixed. Failing (tests and gate stages): - `tests/test_aws_ec2.py::test_the_largest_real_bootstrap_fits_ec2s_cap` - `tests/test_virtual_nodes.py::test_a_regular_nodes_bootstrap_is_byte_identical_to_before_hosts_existed` - `api-unit-dc-test` The whole gate log: artifact `10825` on lane task 10512. Make `develop` pass its full gate again. Open a PR as usual: the merge lane merges a PR that fixes some of these and adds no failure even while `develop` is red.

Fixed red develop: re-pinned bootstrap golden digests (Task 10480 env-twin drop) and moved the tailscale-prefs comment block out of the rendered script, bringing EC2 user-data back under headroom (8205 → ~7540 bytes). Quick gate green; 365 changed-area tests pass. PR #7086 queued. Memory: none applied.