refactor(config): split ParseConfig into tokenise, dispatch, clamp and sanitize helpers

[Maxaubert]

Closes #475

Splits ParseConfig (src/config.cpp, about 260 lines) into static helpers. Move-only, no behaviour change: every key keeps the same parser and clamp, the passes run in the same order, the try/catch stays in ParseConfig.

Extracted functions (src/config.cpp, line ranges after this PR)

Function	Lines	Size	What moved
SanitizeBinds(Config&)	127-158	32	the unsafe-bind and extra-key-switch pass
ClampConfig(Config&, bool haveRenderScaling)	161-230	70	the clamp pass, renderScaling migration (#456), model fallback
ApplyValueKey(Config&, key, val, bool& haveRenderScaling)	235-364	130	both if/else key chains (still two chains, C1061)
ApplyEmptyableKey(Config&, key, val)	367-385	19	the exe lists and engine* keys that accept an empty value
SplitIniLine(line, key&, val&)	388-397	10	trimming, comment/blank skip, key/value split
ParseConfig (what is left)	399-417	19	BOM strip, the loop, the try/catch, the two passes

One commit per extraction; review with git diff --color-moved=dimmed-zebra --color-moved-ws=allow-indentation-change.

How move-only was checked

A moved-lines diff against origin/main (removed vs added lines as a multiset, indentation ignored). The only lines that are not pure moves:

• the new function signatures, their one-line header comments, closing braces and the call sites;
• continue -> return true in ApplyEmptyableKey (the caller continues on true) and continue -> return false in SplitIniLine (the caller continues on false);
• std::string key = ... / std::string val = ... -> assignments to out parameters (the caller declares key, val per line);
• two comments that said "below" now name ParseConfig / ApplyValueKey.

Deliberately not done

• No key -> parser table. It would rewrite every one of the ~130 branches (not move-only), several keys are special (txSamplingMode folding, renderScaling flag, outlineColor pre-parse, the *On switches, hitchThresholdPct clamp-at-parse), and the review leaves this to the separate config-registry (X-macro) decision.
• Helper order in the file is reverse call order (each was inserted above ParseConfig); not reordered to keep the diff a clean move.

Gates

• build.bat check: pass (only the pre-existing fopen C4996 warnings)
• build.bat test: 643/643 test cases, 98941 assertions, exit 0 (tests/test_config_defaults.cpp and tests/fixtures/config_defaults.txt unchanged)
• build.bat: links Wind.exe and WindTray.exe
• src/config_ui untouched, so no build.bat config / Playwright run.

Docs: docs/architecture/08-config-profiles.md (Parsing) now names the helpers; 09-settings-ui.md points a new setting at ApplyValueKey.

🤖 Generated with Claude Code

https://claude.ai/code/session_01TdjopXZfsUiesYxYLYHEdH