build: bin/codeaf is ~9 MB over SIZE-BUDGET on dev, and the size step only reports it

[AbirAbbas]

What happened

On dev@49ad17f12, make build produces a stripped bin/codeaf of 66,478,345 bytes on linux/amd64, against SIZE-BUDGET = 57,400,000 (set in #1488 on 2026-09-25). make size, and so make check, fail on a clean dev tree:

bin/codeaf is 66478345 bytes. The budget in SIZE-BUDGET is 57400000. Over by 9078345.

Nothing on CI goes red, because the size (informational) job in ci-full.yml only prints the number. Its log shows the drift: main@e44650715 weighed 57,921,801 bytes; dev@837b2b06a (2026-09-27) already weighed 65,712,393; dev@f769be412 weighed 66,466,057.

The wording is also stale. Makefile (the size target's message) and ci-full.yml still say the budget was set on linux/arm64. #726 proposed moving that to darwin/amd64 and has been closed as out of date.

Replication

Deterministic (no model).

git checkout origin/dev && make size

Acceptance

• One decision recorded in PERF.md: either raise SIZE-BUDGET to the measured weight and say what spent the ~9 MB between 2026-09-25 and 2026-09-27, or shrink the binary back under 57,400,000.
• The Makefile and ci-full.yml text names the platform the number is measured on, and it is the platform the budget was actually set on.
• make size passes on a clean dev tree.