fix(awk): newline continuation after control headers, regex operands

[chaliy]

Requested by Михайло · project thread

What changed

Three awk fixes found by replaying recorded agent calls (gap telemetry, #2552):

• A newline after the ) of an if/for/while header, after else/do, &&, || or , continues the statement, as POSIX awk's grammar allows. do body; while (...) accepts the ;.
• A regex rule pattern can be one operand of &&, || or ?: (/=/ && !/^#/ { ... }).
• A bare /re/ inside an expression means $0 ~ /re/. It evaluated to the pattern text, which is always true.

Why

awk: unexpected character: ; was the most frequent awk failure in the replay corpus (22 distinct agent scripts): any multi-line awk program with a for (...) or if (...) body on the next line failed. The bare-regex bug was silent: if (/^\[/) matched every line.

Before

$ awk 'BEGIN { for (i = 1; i <= 2; i++)
    print i }'
awk: unexpected character: ;
$ printf 'a=1\n#c\n' | awk '/=/ && !/^#/'
awk: unexpected character: &
$ printf '[s]\na=b\n' | awk '{ if (/^\[/) print "section:" $0 }'
section:[s]
section:a=b

After

1
2
a=1
section:[s]

Matches mawk on all new tests.

Risk

Low. The newline change only affects newlines that POSIX treats as continuations; regex arguments to sub/gsub/match/gensub/split and ~ operands still get the pattern text. Full lib and integration suites pass.

Checklist

• Unit tests (3 new), checked against mawk
• cargo fmt, cargo clippy -D warnings
• knowledge/log.md

https://claude.ai/code/session_019aFikmptPc91Fj4N2iDXQA

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