Support pausing inputs

[wkozyra95]

Intended primarily for mp4 input. It might lead to weird behaviors with other inputs, especially if they have any type of adaptive buffer

[wkozyra95]

I know that this should be an enum, but this will need rework regardless if we add some more options

[Copilot]

Pull request overview

Adds an API endpoint to pause/unpause an input (primarily intended for MP4) and wires it through the pipeline into the core audio/video queues by applying a pause-driven PTS offset.

Changes:

• Add /api/input/{input_id}/update with UpdateInputRequest { pause?: boolean } and register it in OpenAPI generation.
• Implement pause/unpause in smelter-core queues via a shared PauseState that offsets PTS after unpausing.
• Extend the integration-test demo CLI to call the new update-input endpoint.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tools/src/bin/generate_from_types.rs	Registers the new route handler for OpenAPI generation.
tools/schemas/openapi_specification.json	Adds the new endpoint and UpdateInputRequest schema.
src/routes/update_input.rs	New Axum handler + request type for updating (pausing) an input.
src/routes.rs	Wires the new /:id/update route under /api/input.
smelter-core/src/queue/video_queue.rs	Adds pause handling for video (freeze last frame + PTS offset on enqueue).
smelter-core/src/queue/audio_queue.rs	Adds pause handling for audio (skip output while paused + PTS offset on enqueue).
smelter-core/src/queue/utils.rs	Introduces PauseState utility for pause tracking and accumulated PTS offset.
smelter-core/src/queue.rs	Adds Queue::{pause_input, unpause_input} entry points.
smelter-core/src/pipeline/instance.rs	Adds Pipeline::update_input that delegates pause/unpause to the queue.
integration-tests/examples/demo/smelter_state.rs	Adds demo CLI workflow to pause/unpause inputs via the API.
integration-tests/examples/demo/main.rs	Adds “Update input” action to the demo menu.
.claude/skills/api-change/SKILL.md	Updates the API-change checklist to include route registration in OpenAPI paths.

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