feat(coverage): reconstruct exact-base uv workspaces without local-package leakage #750

Buyer-visible problem

The central coverage sandbox can now export a nested standalone pyproject.toml/uv.lock pair, but a true uv workspace may require member project metadata in addition to the root files. Reconstructing only the root pair can make a valid modular repository fail its central review, while silently ignoring missing members would produce incomplete dependency evidence.

This is a central MSA concern: each product and service must remain independently usable, while the organization review plane must also understand a repository that composes several standalone modules through a uv workspace.

Required design

• Read the root uv.lock, root pyproject.toml, and every workspace member/exclusion only from one validated 40-character base commit SHA.
• Parse TOML with Python tomllib; do not execute project code or import project packages.
• Expand workspace member patterns against the exact base tree with anchored POSIX semantics.
• Reject absolute paths, .., control characters, unsafe glob constructs, symlinks, submodules, duplicate members, and paths outside the workspace root.
• Materialize only the metadata required for uv export; document every copied file class.
• Use the pinned, checksum-verified Astral uv executable and the isolated environment defined by fix(coverage): materialize trusted uv lock dependencies #743.
• Export the complete third-party closure for all workspace members with reviewed --all-packages semantics while omitting the root and all local workspace packages (--no-emit-workspace or an equivalently verified contract).
• Keep --frozen, --offline, cacheless execution, dotenv suppression, and managed-Python-download prohibition.
• Reject nonempty output unless every logical line is an exact package == pin with complete SHA-256 hashes.
• Fail closed on missing required member metadata, stale workspace locks, unsupported local source forms, or exporter errors.

Realistic verification

• Standalone nested project remains supported and unchanged.
• Root project plus two workspace members exports the union of third-party dependencies exactly once.
• Virtual workspace without a root [project] exports all members.
• Excluded members are not reconstructed or exported.
• Member globs cannot escape the root or traverse symlinks.
• Local workspace packages never appear as path/direct/editable requirements.
• A missing member pyproject.toml fails before coverage execution.
• An actual BandScope-style nested analysis service remains a passing integration fixture.
• A true multi-member temporary uv workspace is exported with the pinned real uv binary in a bounded integration test.
• Production statement and branch coverage remain 100%; all production symbols retain docstrings.

Documentation and standards

Record the design in docs/doctoring/ with APA 7th references to current Astral uv workspace/export documentation and the approved SLSA 1.2 specification. State the precise conformance boundary; do not claim a SLSA level solely from these controls.

Sequencing

Land the standalone uv materialization baseline in #743 first. Implement this workspace slice as a separate reviewed PR so the broader metadata surface cannot dilute the standalone trust boundary.