feat(#3674): extract shared file-overlap wave partitioner (#4166)

* test(#3674): characterize existing wave-dispatch output and add tests for the extracted partitioner

Pins resolveWaveDispatch's and emitWorkflowScript's current, unextracted
output (chain-overlap, disjoint-empty-set, and a multi-wave/multi-stage
golden script) as a regression safety net ahead of extracting
partitionStages into a standalone module. Also adds the new module's
unit and property tests (test matrix rows 1-11) against its expected
public API, which does not exist yet and is added in the next commit.

* feat(#3674): extract file-overlap partitioner into a shared, generic module

Moves partitionStages' greedy first-fit file-overlap algorithm into a new,
dependency-free src/file-overlap-partitioner.cts module (partitionByFileOverlap),
generalized over a plain {id, files}[] shape rather than claude-orchestration.cts's
Plan/Wave interfaces. partitionStages becomes a thin adapter mapping its own
Plan[] shape onto the generic input and back — behavior-preserving, no dependency
ordering, no path normalization, no filesystem access moved or added. Enables a
future consumer (quick-batch, #3675 / ADR-1239) to reuse the same primitive
without pulling in orchestration internals.

* docs(#3674): register the file-overlap-partitioner module bookkeeping

New src/*.cts -> bin/lib/*.cjs modules need four hand-maintained
registrations beyond the code itself: .gitignore (compiled artifact),
eslint.config.mjs (ADR-457: lint the .cts, not the emitted .cjs),
docs/INVENTORY.md's CLI Modules roster row (regenerated via
gen-inventory-manifest.cjs --write), and a CONTEXT.md glossary entry
matching the convention set by similarly-scoped leaf modules
(text-lines.cts, plan-dependency-graph.cts, spec-section.cts).

* fix(#3674): alphabetize INVENTORY.md row, manifest regen no-op, fast-check import already correct

- docs/INVENTORY.md: move file-overlap-partitioner.cjs row to alphabetical position
- docs/INVENTORY-MANIFEST.json: regenerated via gen-inventory-manifest.cjs --write,
  produced no diff (manifest is keyed by content, not row order)
- tests/claude-orchestration.test.cjs's direct require('fast-check') is correct as-is:
  tests/helpers/fast-check-setup.cjs's own docstring scopes the shared-seed wrapper to
  "every *.property.test.cjs file"; claude-orchestration.test.cjs is not a .property.test.cjs
  file, and every .property.test.cjs file sampled uses the wrapper consistently. No outlier.

* fix(#3674): constrain the no-overlap property test to unique ids, fixing an ambiguous duplicate-id reconstruction

The `no two plans in the same stage share a modified file` property
reconstructs which physical item produced each output id via
`remaining.findIndex(r => r.id === id)`. Under duplicate ids (an
explicitly-supported input shape for `partitionByFileOverlap`) that
reconstruction can pick the wrong physical occurrence, producing a
false-positive overlap failure (observed counterexample: p0(f1),
p208(f1), p208([]) — correctly staged as [[p0,p208#2],[p208#1]], but
misread by id-order as [[p0,p208#1],...], which do overlap).
Properties (a) determinism and (b) totality already exercise
duplicate ids correctly and are left unchanged; only this property's
generated items are now constrained to unique ids via
`fc.uniqueArray`, where the reconstruction is unambiguous.

---------

Co-authored-by: sim <sim@local>

docs/INVENTORY-MANIFEST.json

@@ -379,6 +379,7 @@
       "external-job.cjs",
       "fallow-runner.cjs",
       "federated-config.cjs",
+      "file-overlap-partitioner.cjs",
       "frontmatter.cjs",
       "gap-checker.cjs",
       "gate-predicate-evaluator.cjs",