feat(project): add RuntimeEntry, MetadataConfig, runtimes and metadata fields (M2 T2-1)

[JesuFemi-O]

What this does

This is the first PR in the M2 stack. It teaches tycoon.yml about two things it currently has no concept of:

1. runtimes: — a named map of ingestion runtimes. Each entry says which tool owns a given pipeline (dlt-managed, dlt-project, fivetran, airbyte, or estuary) and, for self-managed dlt projects, where on disk the pipeline lives.
2. metadata: — where tycoon stores its internal state database (run history, source records). Defaults to a local DuckDB file at .tycoon/metadata.duckdb.

Both fields are fully optional with defaults, so every existing tycoon.yml loads without any changes needed. This is a pure schema addition — no command behaviour changes.

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Files touched

File	What changed
src/tycoon/project.py	Added RuntimeEntry and MetadataConfig models; added runtimes and metadata fields to TycoonProject; added Literal to imports
tests/test_project.py	Added TestRuntimesAndMetadata class with 3 new tests

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New models

class RuntimeEntry(BaseModel):
    type: Literal["dlt-managed", "dlt-project", "fivetran", "airbyte", "estuary"]
    path: str | None = None  # only used by dlt-project runtimes

class MetadataConfig(BaseModel):
    backend: str = "duckdb_file"
    path: str = ".tycoon/metadata.duckdb"

backend is a plain str (not Literal) so adding new backends later requires no schema changes.

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Tests added

Test	What it covers
test_existing_yml_loads_without_new_fields	A yml with no runtimes/metadata keys loads cleanly and gets correct defaults
test_runtimes_field_parses	runtimes: block with dlt-managed, dlt-project (with path), and fivetran entries all parse correctly
test_metadata_field_parses	metadata: block with custom backend and path overrides the defaults

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CI checks (run locally)

• ruff check src tests — clean
• pytest — 686 passed, 3 skipped (73.26% coverage, floor is 68%)
• mkdocs build --strict — exit 0
• No new dependencies, uv.lock unchanged

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Stack position

This is M2 T2-1 (#90). The next PR in the stack (T2-2, #92) adds the schema migration helper and will target this branch.

Closes #90

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Closes #90

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.

[db-tycoon-stephen]

Backward compatibility holds — I checked that a tycoon.yml containing nothing but name: still loads, with runtimes == {} and the metadata defaults applied. The three new tests cover the parse paths well.

Two things I'd tighten:

MetadataConfig.backend should be a Literal, not str. RuntimeEntry.type is Literal[...] and rejects bad input at parse time, but backend is a bare str — so backend: duckdb-file (hyphen instead of underscore) validates fine and fails somewhere further downstream. The docstring already says duckdb_file is the only supported backend in v0.1.x, so Literal["duckdb_file"] just makes the model agree with it.

Nothing enforces path for dlt-project runtimes. The comment says path is only meaningful for dlt-project, but a type: dlt-project entry with no path parses cleanly and only breaks when something tries to resolve it. A model_validator(mode="after") requiring path when type == "dlt-project" — and arguably rejecting it for the cloud-managed types — turns that into a clear config error at load.

Neither case has a test. Worth adding negative tests for both, plus one asserting an unknown type: is rejected.

Unrelated to the feature: the project.py reformatting in this diff is fallout from the format pass in #174 missing that file, which is why this reads as +91/-39. Nothing to fix here if #174 picks up ruff format --check.

[db-tycoon-stephen]

Requesting changes on the items in the comment above: make MetadataConfig.backend a Literal["duckdb_file"] to match how RuntimeEntry.type is typed, enforce path for dlt-project runtimes via a model validator, and add negative tests for both plus an unknown type:.

Backward compatibility is solid — verified a name:-only yml still loads with the new defaults.

[JesuFemi-O]

Deferring the two requested changes for now:

MetadataConfig.backend as Literal["duckdb_file"] — keeping it as str intentionally. The design decision going in was that backend should stay flexible as additional backends land. Locking it to a Literal now means a follow-up PR to widen it again each time a new backend is added. The RuntimeEntry.type field is Literal because those are the only ingestion runtime types in scope; backend is expected to grow, so str with a documented default is the right shape for now.

Model validator enforcing path on dlt-project runtimes — agreed this is the right thing to do, deferring to a follow-up issue after M2 closes rather than block the stack on it. Will file the issue.

[db-tycoon-stephen]

Both deferrals make sense — your call on the design intent here, and neither field is consumed anywhere in src/ yet, so there's no user-facing exposure in the meantime. Clearing my changes-requested.

Drop a link to the dlt-project path validator issue on this thread once it's filed and I'll pick it up from there.

[db-tycoon-stephen]

Approving — deferrals accepted, see comment above.

[JesuFemi-O]

Filed #176 to track the dlt-project path validator.