test(kinds): route kind-URI literals through the constants

[akesling]

Stacked on #132 — review that first; this targets its branch and will retarget to main when it merges.

Why

Minting a kind version restates its URI in a lot of places. Before this, a mint touched ~16 files and 43 lines spelling the version, most of them test literals and registration glue re-spelling a URI that PATH_KIND_AGENT_CODING_SESSION already holds. That is the sort of duplication that lets a typo pass its own tests.

What

Tests and registration glue now go through the constants (and BUNDLED_KINDS for "newest") instead of restating the version, across toolpath::{types,jsonl}, toolpath-convo::derive, and path-cli::{kinds,cmd_kind,schema,query} plus tests/query.rs. Tests that deliberately pin older versions keep using …_V1_1_0 / …_V1_0_0, and stored fixture documents are left alone — a document's kind URI is data, not a shared string.

Two tests remain deliberately literal, for opposite reasons:

• One pin test in toolpath::types spells the current URI in full, so a typo in the constant cannot self-validate through every test that consumes the constant.
• A new coherence test in path-cli::kinds binds each bundled entry together: the schema's $id and meta.kind const match the entry's URI, the URI's name/version segments match the entry's fields, the compiled-in bytes match the on-disk kinds/<name>/<version>/schema.json, and the newest entry equals the constant. It was mutation-tested during review — pointing a bundled entry at the wrong version's schema fails it.

path-cli's kinds module becomes pub so the integration test can iterate BUNDLED_KINDS, matching the existing pub-for-tests precedent in that crate (harness, cmd_resume).

Net effect: a future mint touches the constant, the schema file, its BUNDLED_KINDS entry, the site page, and the changelog — the version literals that remain are all genuine mint touchpoints.

Testing

Full workspace suite, clippy, rustdoc, and the examples gate green on the stack. No behavior change: production code paths already flowed through the constants; this is tests and registration glue only.

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