Add API reference and guides under doc/

[laruence]

Summary

Yaf has been carrying an old Chinese manual (doc.laruence.com-era HTML) with known transcription errors (e.g. isOption vs isOptions, geModules) and no documentation for 3.3.x behavior changes. This adds a fresh manual under doc/ built on two guarantees:

• Signatures are never hand-written. All class/method signatures are generated via Reflection from the loaded extension, so they match exactly what the C code registers.
• Prose is cross-checked against 3.3.8-dev sources, including recent fixes: yaf.forward_limit=0 now clamps to the default (previously an infinite loop), Dispatcher::getInstance() requires an initialized Application, Session resolves $_SESSION from the symbol table on every access.

Contents

Section	What's in it
classes/	38 class/interface pages, 233 own methods — each with description, param notes, return semantics and runnable examples
guides/quick-start.md	minimal working app from scratch
guides/lifecycle.md	full request path with plugin-hook timeline (verified against YAF_PLUGIN_HANDLE call sites)
guides/directory-conventions.md	class-name → file-path mapping rules (verified against yaf_loader.c)
guides/routing.md	6 built-in routes, selection matrix, custom routes, URL assembling
guides/error-handling.md	throwException × catchException behavior matrix, error-code ↔ exception table
constants.md / ini.md	all YAF_ERR_* constants and ini directives with defaults
llms.txt / llms-full.txt	AI-friendly entry points (index + full-manual single file)

Descriptions are in Chinese; signatures and examples are language-neutral. Prose lives in doc/annotations/ separated from signatures, so the two can evolve independently.

Test plan

• Read through doc/guides/lifecycle.md and doc/guides/directory-conventions.md (the two most source-sensitive pages)
• Spot-check a few class pages against current sources
• Verify markdown renders cleanly on GitHub