[MarcusKainth]

What this changes, and why

Most of a test job's setup time goes to downloading the workspace test archive, and build-tests spends a minute and a half uploading it. The archive is 2.63 GB, and almost all of it is DWARF: a driver test binary is about 465 MB with full debug info and about 9 MB without. This PR builds the archive with CARGO_PROFILE_TEST_DEBUG=0. The variable is set on the build-tests job, so rust-cache keys on it.

A failing test reports the same thing it does now, because the panic message and its file and line come from the panic location, and debug info doesn't carry that. A RUST_BACKTRACE backtrace names functions but gives no lines.

line-tables-only would keep backtrace lines, but it leaves the archive at 860 MB (measurement run 36121287631, below).

Evidence

Measurement (throwaway PR #583, closed)

The same archive command under each setting, one runner per variant. The size is ls -l tests.tar.zst:

run 36121287631, cold cache	compile	archive
full debug info (main)	10 m 51 s	2,631,156,768 B
line-tables-only	9 m 11 s	862,464,538 B
CARGO_PROFILE_TEST_DEBUG=0	8 m 15 s	186,629,387 B

run 36122853256, warm cache	compile	archive step	upload	download
full debug info (main)	6 m 15 s	402 s	78 s	54 s
CARGO_PROFILE_TEST_DEBUG=0	4 m 21 s	264 s	3 s (level 0)	4 s

This PR's CI run 36122982586

Attempt 1 ran with a cold cache, because the new variable changes rust-cache's key. Attempt 2 reran build-tests and its dependents against the cache attempt 1 saved:

Cache Key:
    v0-rust-build-tests-Linux-x64-3f7eabcb-b396b1ba
  - CARGO_PROFILE_TEST_DEBUG
Restored from cache key "v0-rust-build-tests-Linux-x64-3f7eabcb-b396b1ba" full match: true.
    Finished `test` profile [optimized] target(s) in 4m 26s

	before: run 36116301376 (main code, PR #580)	this PR, attempt 2
test-archives artifact	2,632,939,881 B	191,650,427 B
Archive the suites	448 s	316 s
Upload the archives	83 s	6 s
Download the test archives, per group	33 to 363 s	3 to 7 s
Start the pinned ClickHouse, per group	15 to 18 s	15 to 24 s

Every group passed on both attempts, and ci-passed succeeded.

A panic's location survives debug = 0 (scratch crate, local):

$ CARGO_PROFILE_TEST_DEBUG=0 cargo test -q
thread 'fails' panicked at src/lib.rs:4:5:
assertion `left == right` failed: the value
  left: 2
 right: 3

$ make actionlint zizmor; echo "exit=$?"
No findings to report. Good job! (10 suppressed)
exit=0

Invariants

None. CI build settings only; no SQL and no computation path changes.

Spec impact

• None. No contract in SPEC.md is touched

Checks

• make gates: not run locally. CI's lint job ran make lint and every test group passed
• No AI attribution trailers in the commits

Written mostly by Claude Opus 5.5.