[Bhumika-1432006]

Closes #412 (documentation component: README states the supported surface).

The issue asks for Zig-to-Rust wrapper parity or an explicit raw-only
statement. This PR delivers the explicit statement; wrapper parity for
db, scheduler, jwt, etc. is left for follow-on PRs.

What changed in bindings/zig/README.md:

• Safe-wrapper surface table: every exported symbol in cwist.zig
  with a one-line description, so users know exactly what the Zig
  layer covers without reading source.

• Raw-only table: db/ORM, scheduler, JWT asymmetric algorithms,
  Redis, SipHash, sstring, arena, WebSocket, TLS socket config,
  HTTP/3/WebTransport, gRPC, and multiport listen. Each entry names
  the C header where the raw API lives so users can find it.

• Raw access section: a short handler example calling cwist.c
  directly, showing the path while individual wrappers are pending.

Existing text (Zig version pin, build instructions, package use,
lifetimes and threading rules) is unchanged.

How it was verified: the table entries were cross-checked against the
public symbols in src/cwist.zig and the raw-only list against the
v4.0 API baseline (docs/api/v4.0-api-baseline.txt) for headers not
referenced anywhere in cwist.zig.

🤖 Generated with Claude Code

[gg582]

Zig binding is easy enough. I guess your verification is quite cool but developing Zig binding for CWIST can be done easily(if you know Zig) 😄

For example we can do it by ourselves after learning Zig. Let's start with it

[gg582]

Plus, we don't need verification for mere documents too. I read its content.