Add `#![deny(missing_docs)]` across multiple crates and fill in
documentation for all public items, including struct fields, enum
variants, trait methods, and proc macros.  Also mark two shell scripts
as executable.

Use Option for load_pathf_map return type and emit a descriptive
compile_error when the type mapping file cannot be loaded, guiding users
to set up build.rs correctly

macros

Reintroduce `r_print!` and `r_println!` macros as public exports, now
supporting both explicit buffer argument and implicit `#[buffer]` attr.
Add `#[buffer]` attribute macro that wraps unit-returning functions to
produce a `RenderResult` with an automatically injected buffer variable.
Relax `RenderResult::print()` and `println()` to accept `impl
AsRef<str>`.

Refactor #[chain], #[renderer], #[help], and #[completion] macros to
keep
the original user function as a named item instead of inlining its body.
Trait method implementations now call the original function by name,
injecting resources from the application context.

This improves debugging (stack traces reference user function names),
error messages, and macro expansion clarity.

Move routing methods exclusively to the `Routable` trait and update
all macro-generated code to reference `Routable` instead of `Grouped`

Use the span of the `?` token when generating the macro invocation in
the `#[routeify]` transformation, so that rust-analyzer resolves hover
and go-to-definition on `?` to the `route!` macro's documentation