lib: α-batch-2 rt.malloc → alloc([], N)! (path/shlex/fmt/ostest)
Phase 0 #8 second α-batch. 7 sites: lib/path/path.ww `join` ×4,
lib/shlex/shlex.ww `dupstr`, lib/fmt/fmt.ww `asprintf` tight-copy,
lib/os/ostest.ww `test_alloc_free_roundtrip`. Same dup-pilot pattern
(4c07ef0, 47918d3): `alloc([], N)!` + `buf.len = N;` +
`return strings.frombytes(buf);`.
Side effects:
- path/shlex/fmt: import switches `rt` → `strings` (callers now
reference `strings.frombytes`, not `rt.malloc` direct).
- ostest.ww: `import rt;` retained — the alloc builtin lowers to
`CALL malloc(SB)` which resolves via rt's @symbol("rt_malloc")
decl. Other files reach rt transitively via `import strings`;
ostest only imports os, so it needs the explicit rt import.
- shlex stale comment "avoid strings dep" stripped — strings is now
in scope.
Verified make test 132/132 + 995_self_rebuild byte-identity.
Advances #43.
Hojun-Cho
00d88ff9fc