refactor(flows): wire the semantic shape through PaperFlow.build and deprecate paper_flow #139

Current state

quantmind/flows/paper/__init__.py exposes two entry points for building paper knowledge artifacts, and they disagree on which one is canonical.

• PaperFlow(cfg).build(input) is the config-bound flow. It dispatches on the cfg type, but only PaperStructureCfg -> PaperStructureTree is wired. Any other cfg type (including PaperFlowCfg) raises NotImplementedError.
• paper_flow(input, *, cfg) is a standalone function that still owns the semantic chunk/summary shape (PaperFlowResult) — the fetch/parse, chunking, and bounded map-reduce summary pipeline live in its body.

The module docstring and the architecture constraint both say the cfg type should select the knowledge shape a single config-bound flow produces (PaperFlow(cfg).build(input), typed dispatch, not a hierarchy). Today the semantic shape sits outside that dispatch, so the two shapes are reached through two different call styles, and paper_flow is a second implementation rather than a thin wrapper.

Target

PaperFlow.build becomes the single config-bound entry for both paper shapes, selected by cfg type:

• PaperStructureCfg -> PaperStructureTree (unchanged)
• PaperFlowCfg -> PaperFlowResult (moved in from paper_flow)
• any other cfg type -> NotImplementedError

paper_flow becomes a deprecated thin wrapper: it emits a DeprecationWarning and delegates to PaperFlow(PaperFlowCfg(...)).build(input). It is kept — not removed — because it is grandfathered by the operation-naming contract (contexts/design/operations/naming.md); its signature stays (input: PaperInput, *, cfg: PaperFlowCfg | None = None) so the magic-input introspection path is unaffected.

The semantic-shape logic moves rather than being duplicated, so there is one implementation of the chunk/summary pipeline.

Migration notes

• Callers move from await paper_flow(input, cfg=PaperFlowCfg(...)) to await PaperFlow(PaperFlowCfg(...)).build(input). batch_run(flow.build, inputs) is the intended batch shape under one bound setting.
• build's return type depends on the bound cfg type; the implementation keeps typing precise under basedpyright standard mode so each shape's callers keep their exact result type.
• No public behavior of either shape changes; this is a type: refactor. Tests, the paper example, the paper flow design page, and the component catalog row are updated to the config-bound entry point, and a test covers the paper_flow deprecation warning and delegation.