refactor(whip): split whip.rs and whip_session_manager.rs into sub-modules

[wagenet]

Written by Claude (Claude Code) on behalf of @wagenet.

Description

Splits the two WHIP files that were over the 1500-line threshold into directory modules, following the pipeline/ and vision_mixer/ pattern. #756 committed to doing this separately, before #792.

Layout

File	Lines	Holds
blocks/builtin/whip.rs (before)	3141
whip/mod.rs	138	WHIPOutputBuilder, WHIPInputBuilder, re-exports
whip/slot_chain.rs	895	build_whipserversrc and its per-slot caps, decodebin, damage-probe and output-stamp helpers
whip/watchdog.rs	259	per-session inactivity watchdog
whip/session.rs	1097	create_whipserversrc_for_session, CreatedSession, keyframe recovery logging, the appsink→slot bridge and its video PTS ordering
whip/output.rs	464	WHIP Output (whipclientsink, whipsink, incoming-RTP handler)
whip/definition.rs	350	block definitions
whip_session_manager.rs (before)	1841
whip_session_manager/mod.rs	569	WhipSessionManager: registry, cleanup task, removal
whip_session_manager/endpoint.rs	231	WhipEndpointConfig, SlotDecodebin, slot allocation, SessionCleanupRequest
whip_session_manager/activity.rs	423	ActivityStamp, SessionActivity, StallSide, DECODE_GRACE
whip_session_manager/takeover.rs	454	allocate_slot_or_take_over, idlest_session, the TAKEOVER_* constants
whip_session_manager/test_support.rs	224	fixtures shared by the manager's test modules (#[cfg(test)])

Line counts include each file's tests. Every public item keeps its path through a pub use in mod.rs, so no caller changed.

Generated, not hand-edited

Every other open WHIP PR edits one of these two files, so a hand-made split would have to be hand-merged against each of them. The split is generated instead, and can be regenerated on whatever base it ends up landing on. The generator is on the fork, not in this PR: tools/whip-split on wagenet/whip-split-tool.

1. split.py places every item of the two files by a manifest and moves its text unchanged. It refuses to run if a file has an item the manifest does not place.
2. fixup.py makes the result compile from compiler output alone: it raises to pub(super) exactly the items rustc reports private at a use site, deletes the imports rustc reports unused, and runs cargo fmt.

Running both on this branch's parent reproduces this commit byte for byte.

It is a move

verify.py compares the non-blank lines of the two old files with those of the eleven new ones, leaving out use declarations, leading whitespace and a pub(super) prefix:

• 4 old lines have no match. 2 are the register and receiving_but_stalled fixture signatures, which rustfmt wrapped once pub(super) pushed them past 100 columns. 2 are comments that named whip.rs by path (below).
• Every added line is either those 4 rewritten, or structural: 9 mod declarations, 9 //! module headers, 4 new mod tests { wrappers with their #[cfg(test)] and closing braces, the #[cfg(test)] on mod test_support, and the impl WhipSessionManager { wrapper in takeover.rs.

pub(super) went on 17 items: build_whipclientsink, build_whipsink, wait_for_inactivity, INACTIVITY_TIMEOUT, and 13 fixtures in test_support.rs.

Four comments are the only edits that are not moves. Each named a file that no longer exists:

• backend/static/tests/whip_reconnect.test.js: where INACTIVITY_TIMEOUT lives is now whip/watchdog.rs.
• WhipSession::cleanup_sent doc: "the callbacks in whip.rs" is now whip/session.rs.
• DECODE_GRACE doc: the compile-time assertion is in whip/watchdog.rs.
• gst/pipeline_bridge.rs test_support doc: the call-site test is in whip/session.rs.

Related Issue

None. Follow-up committed to in #756.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Refactor only: no behaviour change.

Checklist

• I have run cargo fmt --all
• I have run cargo clippy --workspace --all-targets -- -D warnings
• I have run cargo test --workspace (WHIP tests only, below)
• I have updated documentation as needed (none needed)
• I have added tests for new functionality (no new functionality)

Tests

The old files held 33 unit tests. The same 33 ran and passed in their new modules, matched by name against the test output. Each moved with the code it tests; the manager's takeover and activity tests share fixtures, so those went to test_support.rs.

Run from the workspace root on this branch:

• cargo fmt --all -- --check: clean
• cargo clippy --workspace --all-targets -- -D warnings: clean
• cargo test --lib -- whip pipeline_bridge: 44 passed, 0 failed (the 33 moved tests plus other WHIP and pipeline_bridge tests)
• cargo test on whip_idle_slot_test, whip_session_branch_test, whip_slot_caps_reuse_test, whip_slot_decoder_reuse_test, whip_video_damage_test, whip_whep_ice_transport_policy_test, ice_preflight_test, cors_expose_headers_test, pipeline_lifecycle_test and openapi_test: 31 passed, 0 failed
• node --test backend/static/tests/whip_reconnect.test.js: 8 passed (its comment changed)

Not run: the rest of cargo test --workspace, the suite with --features efp, and the suite on the parent commit. The unchanged test set rests on the per-name match above.

🤖 Generated with Claude Code

[srperens]

Noted as a draft, so I am holding off on a full review until it is marked ready for review. If you want one before then, say so here or request me as a reviewer.

[srperens]

Closing in favour of #1053, which is now merged. It splits whip.rs (and whep.rs) into input/ and output/ sub-modules, which covers the whip.rs part of this PR. whip_session_manager.rs is still one 1841-line file; a split of that would be welcome as a fresh PR on top of the new layout.