[ISSUE-12] Implement bounded full-build executor and material flow

[Gonza10V]

Motivation

• Add a bounded fixed-point full-build executor that orchestrates stage runs, promotes missing dependencies, indexes generated products, aggregates expected blockers/approvals/warnings, and safely terminates on no progress or max iterations, and wire the public API to use planner/executor defaults when not injected.

Description

• Added a lightweight BuildContext dataclass to hold sbol, inventory, build_document, options, and optional adapters/graph/logger (src/buildcompiler/execution/context.py).
• Implemented FullBuildExecutor with a bounded worklist loop, deterministic promotion of missing inputs (promoted ids promoted:<stage>:<sha1-12>), product indexing/deduplication, optional transformation/plating chaining (deduped), and final FullBuildResult aggregation (src/buildcompiler/execution/executor.py).
• Exported execution types from buildcompiler.execution and wired BuildCompiler.plan, BuildCompiler.execute, and module-level full_build to instantiate FullBuildPlanner/FullBuildExecutor when not injected; added clear ValueError when required dependencies are missing (src/buildcompiler/execution/__init__.py, src/buildcompiler/api/compiler.py).
• Minor import fixes to avoid package import cycles by using buildcompiler.api.options where appropriate and small test additions (src/buildcompiler/stages/*, src/buildcompiler/planning/*, src/buildcompiler/inventory/selector.py).

Testing

• Ran unit tests: pytest tests/unit/execution tests/unit/api which passed locally (14 passed, including new tests/unit/execution/test_executor.py).
• Ran linter/format commands for touched files: ruff check / ruff format on the targeted files; ruff format reformatted 3 files and final checks passed for the edited files.
• Noted environment/network limitation when running the full uv toolchain: uv run pytest ... failed due to fetching optional SBOLInventory dependency from GitHub (network/Git access error), so the smallest reproducible commands to verify this PR are the pytest and ruff commands listed above which succeeded locally.

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Codex Task