single-device framegen, pacing overhaul, gen8 mipmaps replaeement

[utkarshdalal]

Reworks the Android path on top of 87f1b93:

• Single-device framegen: the graph adopts the game's VkInstance/VkDevice (initializeExternal/createContextFromImages) instead of a private device sharing AHBs across ICDs, which scrambled memory when the game ran on a different driver than the system one. Barriers route through a sync1 compat path; required features are merged into the game's device create.
• Real fence sync on the input copy (Mini::Fence) replacing a no-op submit; repeated timeouts fall back to passthrough presents.
• Base fps limiter (fps_limit conf key) phase-locked to the display vsync grid published by the app (vsync.txt); generated presents spaced at baseInterval/multiplier with late-slot skip; pause/resume no longer poisons the pacing EWMA (deltas over 250 ms reset it).
• Clean-room mipmaps replacement shader (shaders/mipmaps_replacement.comp, embedded at build time), default on. Mesa's experimental Adreno gen8 backend miscompiles the DLL's translated mipmaps pass (storage writes stop landing after startup, freezing the flow chain); the replacement computes the same luma pyramid without the fragile single-dispatch TGSM design. orig_mipmaps=true restores the DLL translation; a raw .spv next to conf.toml overrides either.
• Diagnostics: stats.txt (measured fps + per-stage timing), debug_dump (frame/flow-chain pixel dumps), debug_inputs passthrough modes, adopted- device capability log.
• Config: hot-apply for fps_limit and debug keys without swapchain recreation; experimental_present_mode conf key (fifo/mailbox/immediate).