QVAC-23713 fix(minimax-h3): preserve tiled decode and effective fps

[aegioscy]

Summary

• restore upstream-compatible tiled MiniMax-H3 VAE decoding to eliminate grid corruption
• propagate MiniMax-H3’s enforced 24 FPS to CLI and server container encoding
• keep the fabric-based QVAC GGML submodule pin unchanged

Test plan

• Build build-cli on macstudio
• Generate a seeded UD-Q2/Q2 H3 clip at 640x384 with default requested FPS
• Confirm output contains 39 frames at 24 FPS and muxed A/V duration is 1.583333 seconds
• Compare first frame against upstream reference: 41.45 dB PSNR; no grid artifacts

[dev-nid]

qvac-ext-stable-diffusion.cpp/examples/server/api.md

Line 1181 in 31749f1

`fps` is request metadata for the generated sequence and is echoed in the completed job result.

This now returns the effective FPS rather than always echoing the requested value. Could we update this sentence to match the behavior and line 1205?

[dev-nid]

Not introduced by this PR. But just posting it

qvac-ext-stable-diffusion.cpp/examples/cli/main.cpp

Line 680 in 31749f1

cli_params.preview_fps = gen_params.fps;

MiniMax-H3 previews still use the requested FPS, while generation and final output use the enforced 24 FPS.

[github-actions]

Review Status

Current Status: ❌ PENDING
Approvals so far: none

Pending reviews: Needs 1 Management or Team Lead, and 1 more from Management, Team Lead, or Member.

[aegioscy]

Addressed the remaining MiniMax-H3 review notes in 7adccbe:

• Updated examples/server/api.md to distinguish requested FPS from the effective playback FPS returned in the result.
• Updated CLI preview encoding to use H3's enforced 24 FPS, matching generated and final output.

The pending approval-status message needs reviewer action and has no code change.

[amangupta-tether]

Just some non-blocking comments