Simplify toolpath format to single Graph root

[eliothedeman]

Summary

• Remove the Document enum and the {"Step":…} / {"Path":…} / {"Graph":…} envelope. Every .path.json file is a Graph at the root; every .path.jsonl file is a single-path Graph at the file boundary.
• Single root type means uniform file shape — one schema, one parser path, no envelope detection across the workspace.

What changed

Core

• toolpath 0.2.0 → 0.3.0: Document removed. New Graph helpers: from_json / to_json / to_json_pretty, from_path, single_path, into_single_path. JSONL helpers on Graph wrap a single inline Path (new JsonlError::NotSinglePathGraph).

Provider crates

• toolpath-git 0.1.3 → 0.2.0: derive returns Graph (single branch → single-path graph; multi-branch → multi-path graph).
• toolpath-pi 0.2.0 → 0.3.0: derive_project returns Graph.

Renderers

• toolpath-dot 0.1.2 → 0.2.0: render(&Graph, …). Single-path graphs use the path layout, multi-path use clusters.
• toolpath-md 0.2.0 → 0.3.0: render(&Graph, …). Same dispatch.

CLI (toolpath-cli 0.5.0 → 0.6.0)

• validate, render, query, merge, import, export, track, cache all operate on Graph at file boundaries.
• export claude / export gemini reject multi-path graphs with a clear error — projection requires exactly one inline path.

Format artifacts

• examples/step-NN.json are now single-path single-step graphs.
• examples/path-NN.path.json are single-path graphs (no envelope).
• examples/graph-01-release.json drops its envelope. All .path.jsonl regenerated.
• schema/toolpath.schema.json collapses the root oneOf of three envelopes into $ref: #/$defs/graph.
• RFC.md, docs/RFC-jsonl.md, README.md, CHANGELOG.md, and per-crate READMEs updated.

Why

The three-variant root forced discriminator logic into every consumer (CLI commands, renderers, schema validators, fixture writers, docs). Collapsing to one root type removes that branching and gives every file a uniform shape — what used to be a bare Step or Path is now a degenerate single-path graph.

Reviewer notes

Mid-way through the change I made a tooling misstep: an early cp partially clobbered two large files. I restored both from HEAD and re-applied just the Document → Graph migration, but it's worth a focused look at:

• crates/toolpath-cli/src/cmd_import.rs — fzf integration restored from HEAD; only Document::* → Graph::* swaps and the doc_summary / doc_inner_id simplifications should appear in the diff.
• crates/toolpath-cli/src/cmd_export.rs — full gemini-export code restored from HEAD; only Document::* → Graph::* swaps plus the new "reject multi-path graph" error path.

Diff vs. main on those two files should show no behavior or feature changes beyond the format migration.

Test plan

• cargo build --workspace clean
• cargo test --workspace — all tests passing across every crate (no failures)
• cargo clippy --workspace -- -D warnings clean
• cargo run -p toolpath-cli -- validate --input <each> passes for all 16 example fixtures (12 JSON graphs + 4 JSONL streams)
• Render-md snapshot tests regenerated under new single-path-graph rendering
• Manual smoke test: path import git → cache → path render dot/md → path validate flow
• Manual smoke test: path import claude --no-cache | path export claude round-trip on a real session

[github-actions]

🔍 Preview deployed: https://db8fdccf.toolpath.pages.dev

[akesling]

LGTM

[akesling]

What is a "release"? Did the LLM eat its tail here?

[akesling]

Not necessary in this PR, but do we want to allow general graph streaming via the JSONL?

[eliothedeman]

yes absolutely

[od0]

LGTM as well