[refactor] v2: use absolute imports (v2.*) everywhere instead of relative

Mechanical conversion of every relative import under v2/ to an absolute v2.* path
(from .x / ..x / ...x -> from v2.<pkg>.x) so imports are unambiguous, grep-able, and
stable when code is copied/moved between entrypoints (VideoGenerator, CLI, server).

Surgical prefix-only rewrite: only the 'from <dots><module>' prefix changed — import
names, parentheses, multi-line formatting, comments, and ordering are byte-for-byte
preserved (no collapsing, no reorder, no unrelated reformatting).

- 471 imports across 125 files; v2/tests/ was already absolute (untouched).
- Validated: all 125 files compile, every 'from v2.* import' target resolves to a real
  module/package, zero relative imports remain (full sweep), CPU mini suite green
  (202 passed, 2 skipped).

v2/loop/__init__.py

@@ -1,8 +1,8 @@
 """Loop plane — driven loops + policies (design_v3 §5)."""
 from __future__ import annotations
 
-from .._enums import LoopKind, WorkUnitKind
-from .contracts import (
+from v2._enums import LoopKind, WorkUnitKind
+from v2.loop.contracts import (
     CacheOp,
     CachePlan,
     Done,
@@ -17,8 +17,8 @@ from .contracts import (
     StepResult,
     WorkPlan,
 )
-from .driver import LoopRunner
-from .sampler import add_noise, build_flow_sigmas, flow_match_euler_step, x0_from_velocity
+from v2.loop.driver import LoopRunner
+from v2.loop.sampler import add_noise, build_flow_sigmas, flow_match_euler_step, x0_from_velocity
 
 __all__ = [
     "Loop", "LoopContext", "LoopState", "LoopResult", "WorkPlan", "Done", "StepResult",

v2/loop/contracts.py

@@ -26,9 +26,9 @@ from __future__ import annotations
 from dataclasses import dataclass, field
 from typing import Any, Protocol, runtime_checkable
 
-from .._enums import ExecutionProfile, WorkUnitKind
-from .._types import TensorLike
-from ..request.streams import StreamChunk
+from v2._enums import ExecutionProfile, WorkUnitKind
+from v2._types import TensorLike
+from v2.request.streams import StreamChunk
 
 
 # --------------------------------------------------------------------------- #

v2/loop/driver.py

@@ -10,7 +10,7 @@ from __future__ import annotations
 
 from typing import Any
 
-from .contracts import Done, LoopContext, LoopResult, LoopState, WorkPlan
+from v2.loop.contracts import Done, LoopContext, LoopResult, LoopState, WorkPlan
 
 
 class LoopRunner:

v2/loop/policies/__init__.py

@@ -1,7 +1,7 @@
 """Policies — the default step decomposition (design_v3 §5.1, §6.2.3)."""
 from __future__ import annotations
 
-from .base import (
+from v2.loop.policies.base import (
     BoundaryTimestepRouting,
     ConditioningInjector,
     ExpertRouting,
@@ -10,7 +10,7 @@ from .base import (
     PassthroughConditioning,
     PrecisionPolicy,
 )
-from .cfg import (
+from v2.loop.policies.cfg import (
     AdaptiveGateCFG,
     BatchedCFG,
     CFGPolicy,

v2/loop/policies/base.py

@@ -15,8 +15,8 @@ from typing import Any
 
 import numpy as np
 
-from ..contracts import StepContext
-from ..sampler import build_flow_sigmas
+from v2.loop.contracts import StepContext
+from v2.loop.sampler import build_flow_sigmas
 
 
 # --------------------------------------------------------------------------- #

v2/loop/policies/cfg.py

@@ -17,7 +17,7 @@ from typing import Any
 
 import numpy as np
 
-from ..contracts import StepContext
+from v2.loop.contracts import StepContext
 
 
 class CFGPolicy(ABC):