parser/lexer: 5.1 error-token quoting + pin break-outside-loop wording (#95, #105)

[ianm199]

Closes #105. Closes #95.

What

Two localized, version-gated parser/lexer wording fixes landed together (they overlap on Lua 5.1's break message).

#105 — 5.1 quotes special near/expected tokens

Lua 5.1's luaX_lexerror / error_expected wrap the whole near/expected token in LUA_QS ('%s') unconditionally, so the special multi-char labels (<eof>, <name>, <number>, <string>) come out quoted. 5.2 rewrote txtToken/luaX_token2str to leave those bare and quote only symbols/reserved/literals. lua-rs implemented the 5.2+ rule on every version, so all 5.1 syntax errors involving a special token diverged by exactly the surrounding quotes.

input (-e)	before (5.1)	after / ref 5.1.5
if	unexpected symbol near <eof>	unexpected symbol near '<eof>'
local	<name> expected near <eof>	'<name>' expected near '<eof>'
return 1 2	<eof> expected near '2'	'<eof>' expected near '2'
break	no loop to break near <eof>	no loop to break near '<eof>'

Seam: snapshot the active LuaVersion onto LexState at lexer setup (the error formatters take only &LexState, so this avoids threading &LuaState through every syntax-error callsite), and quote the token >= TK_EOS arm of token2str_raw for 5.1. Covers both the near-token (lex_error/txt_token) and expected-token (error_expected/token2str) paths. The 5.2+ path is provably byte-identical (token < TK_EOS || version == V51 reduces to the old condition for non-5.1).

#95 — break-outside-loop wording

The wording was already correctly version-gated in breakstat/undef_goto. This PR adds regression tests pinning all five arms so a future refactor can't collapse them, and 5.1's arm picks up its quote from the #105 fix:

• 5.1 (eager, post-consume): no loop to break near '<eof>'
• 5.2 / 5.3 (deferred): <break> at line N not inside a loop
• 5.4 (deferred): break outside loop at line N
• 5.5 (eager): break outside loop near 'break'

Tests

• 6 new cases in crates/lua-rs-runtime/tests/multiversion_oracle.rs covering all 5 versions (the differential oracle); the parser/lexer: 5.1 doesn't quote special near/expected tokens (<eof>, <name>, ...) #105 cases failed before the fix and pass after.
• Full lua-rs-runtime + lua-lex + lua-parse crate suites green.
• Official 5.4 errors / constructs / attrib / goto pass; CLI verified end-to-end across all five versions via LUA_RS_VERSION.

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