lib/ww,wcc: consolidate frontend into one syntax package (Go-compiler model, #74)

The ww compiler frontend was split across packages lex (lex+tok), ww
(ast+sym+typ), and parse — mirroring Hare's ref/hare/hare/{ast,lex,parse}.
That split's only payoff is third-party reuse, which ww has zero of: the
frontend is consumed by exactly one client, the wcc backend. The split's
cost is a wide cross-package export surface — every fn over a sibling
package's type must export it, and under separate compilation that
re-triggers check_exported_type, plus a phantom `import tok;` (tok lives
in package lex). Consolidate into ONE package lib/ww/syntax/, modelled on
Go's cmd/compile/internal/syntax. The 9 files move in (package syntax);
the intra-frontend mutual references become same-package; wcc and the
tool mains import syntax. No cstage C change (the C frontend mangles from
the source package clause). Internal data shapes (AST kinds, token model,
lexer/parser state) still mirror ref/hare/hare per rule 6/12 — only the
module decomposition collapses; the stdlib is untouched.

USER-approved (#74); spec .ai/rob-frontend-reorg.md (drew2 fidelity-
confirmed). Rule-6 carve-out documented in CLAUDE.md. Dissolves the tok
phantom import; collapses the intra-frontend export sprawl. Byte-id
rebaseline (lex.X/parse.X/ww.X -> syntax.X); cs==ww held. The residual
syntax->wcc export surface (10 types) + the unqualified-ref question are
separate follow-ups (#72/#75).

CLAUDE.md

@@ -3,7 +3,7 @@
 3. cmd/ is the C bootstrap toolchain (wcc frontend lib, w6c/w6a/w6l per-arch, ww driver); selfhost/ is the ww reimplementation
 4. All C code must strictly align with plan 9 coding style
 5. lib/ is the standard library; follow Hare APIs (signatures, layout, error idioms) — consult ref/hare/ before designing new modules. Package declaration form is Go-style explicit `package foo;` and imports use `import foo;` (executables declare `package main;`) per language design (rob-pike + plan-9 sensibility); lib/ API surface still mirrors Hare.
-6. ref/hare and ref/plan9front are read-only references — consult before inventing data shapes or syntax
+6. ref/hare and ref/plan9front are read-only references — consult before inventing data shapes or syntax. Carve-out: the ww compiler frontend is ONE package `lib/ww/syntax/` (tok+lex+ast+sym+typ+parse), a deliberate Go-over-Hare departure modelled on Go's `cmd/compile/internal/syntax` rather than ref/hare/hare's `{ast,lex,parse}` split. Rationale: the split's only payoff is third-party reuse (an IDE wanting `ast` without the parser), which ww has zero of — its frontend is consumed by exactly one client, the `wcc` backend. Consolidating dissolves the cross-package export sprawl (a fn over an unexported sibling type re-triggers sep-build's check_exported_type). Rule 6/12 still bind the internal data shapes (AST kinds, token model, lexer/parser state mirror ref/hare/hare); only the module DECOMPOSITION collapses. The surviving export surface is `syntax`'s public API consumed by `wcc` (a small Hare-faithful set). Ref: USER-approved #74; spec .ai/rob-frontend-reorg.md (rob, drew2 fidelity-confirmed).
 7. No workarounds. If a bug forces a workaround, STOP and report with a precise repro. Document any retained divergence at the site with a pointer to the filed task. Never silent.
 8. Comments are WHY-only. Never narrate WHAT the code does — names carry the WHAT. Comment only non-obvious WHY: a constraint, a divergence from a reference, a citation to a filed task.
 9. Hare-fidelity over convenience. No ad-hoc extensions, renames, or convenience wrappers in lib/. Cite ref/hare/<module>/<file> for every signature ported. Carve-out: the Hare `_unsafe` suffix convention is dropped wholesale (ww is C/Plan-9-lineage, an unmanaged systems language — no GC, no "safe" baseline to be unsafe relative to). bytes→str is a pure reinterpret (`strings.frombytes`, renamed from Hare's `fromutf8_unsafe`); validation is opt-in via `utf8.validate(b)?` at the IO source, never wrapped per-construction. Rationale: ref/hare/strings/utf8.ha:10,22 — the suffix flags Hare's managed-bytes-safety axis, which ww doesn't have. The honest name (`frombytes`) reserves `fromutf8` for a future true validating helper. Carve-out: lib/ tests use Go's external-test-package idiom (`package <mod>_test;` + `import <mod>;`), a sanctioned Go-over-Hare departure — ww hard-rejects self-import (full Go), and Hare's same-package `@test` colocation now has a ww analogue: in-package white-box `@test` files (`package <mod>;`, colocated) are sanctioned alongside the external black-box `package <mod>_test;` split — Go's `foo`/`foo_test` model — now that the non-T `@test` drop landed (#6, harec check.c:3941, 08a76cf; #5 closed). Rule 5/9 binds lib/ *API* surface, not test-authoring style. Ref: Go `foo_test` convention; task #16.