fix: close remaining 0.1.0 release gaps

[tisonkun]

Summary

This is a narrow 0.1.0 release audit, limited to issues with a reproducible downstream failure or an unambiguous release-facing mismatch.

• preserve valid type-qualified Serde paths such as <T as Trait>::function as parseable Rust token streams, relying on proc_macro2's round-trip contract instead of maintaining a whitespace formatter
• keep zero-length array fields bound-free inside generic derives, matching the existing [T; 0] shape contract
• point the README and rustdoc installation snippets at the upcoming 0.1.0 release
• record that generic-bound traversal follows Serde's deliberately selective implementation so it is not incorrectly replaced by a visitor that enters macros and const expressions

Review order

The commits are intentionally small. The fourth commit is an additive correction to the first one after review; history was not rewritten. Each commit message contains a Why: paragraph describing the concrete user failure or maintenance risk.

1. fix: preserve qualified Serde paths
2. fix: avoid empty-array element bounds in derives
3. docs: target installation examples at 0.1.0
4. fix: preserve parseable path metadata
5. docs: identify the derive-bound reference

Deliberate non-changes

The broader "not invented here" audit did not find another production implementation that could be replaced without increasing risk:

• generic-bound inference remains an explicit AST walk because serde_derive::bound::with_bound uses the same selective approach; a general syn::visit::Visit would enter macro and const-expression syntax and can infer spurious shape bounds
• paired package verification keeps its unpack-and-patch step because applying Cargo's patch during cargo package conflicts with --locked at the workspace-resolution stage
• the small cargo metadata JSON lookup remains local; adding cargo_metadata would add more dependency and API surface than it removes
• graph recursion identity, union normalization, and built-in shapes are domain behavior rather than substitute implementations; built-ins must mirror Serde explicitly because orphan rules prevent deriving them for foreign standard-library types

The audit also found no evidence for deleting existing behavior-boundary tests, changing the public graph model, adding format policy, or expanding built-in coverage speculatively.

Validation

• cargo x build --locked
• cargo x test
• cargo x lint
• cargo x package --locked
• cargo +1.85.0 x test
• cargo +1.85.0 check -p serde-shape --lib --no-default-features --target thumbv7em-none-eabihf
• cargo +1.85.0 check -p serde-shape-test-no-std --lib --target thumbv7em-none-eabihf
• cargo semver-checks check-release -p serde-shape --baseline-rev origin/main --release-type patch --all-features (223 checks passed)