docs: refresh v0.1.42 prep references and draft notes (br-bd-erc)

Author: dmoliveira

docs/changelog.md

@@ -105,3 +105,8 @@
 - Release published: `https://github.com/dmoliveira/loopmux/releases/tag/v0.1.41`.
 - Tag: `v0.1.41`.
 - Preflight and publish checks passed: `cargo fmt --check`, `cargo test -q` (143 passed), `cargo clippy -- -D warnings`, `make smoke-post-release`.
+
+### v0.1.42 Prep References
+- PR #158: Kick off v0.1.42 milestone and release scaffolds (`https://github.com/dmoliveira/loopmux/pull/158`)
+- PR #159: Add poll interval context to heartbeat diagnostics (`https://github.com/dmoliveira/loopmux/pull/159`)
+- PR #160: Add heartbeat metric output contract regression (`https://github.com/dmoliveira/loopmux/pull/160`)

docs/release/v0.1.42-draft.md

@@ -8,10 +8,10 @@
 - Added `docs/plan/v0.1.42-milestone.md` to define scope and acceptance criteria.
 
 ## Changes
-- TBD: summarize runtime signal refinements merged during v0.1.42.
+- Added explicit poll interval context (`poll=<n>s`) to heartbeat diagnostics while preserving existing activity/progress/window semantics.
 
 ## Fixes
-- TBD: summarize cadence and control-path regression fixes merged during v0.1.42.
+- Added heartbeat output contract regression coverage to protect required telemetry keys across running/holding/stopped states.
 
 ## Validation
 - `cargo fmt --check`
@@ -20,6 +20,9 @@
 
 ## Included Pull Requests
 - `#157` Post-release: bump to 0.1.42-dev and log v0.1.41 evidence
+- `#158` Kick off v0.1.42 milestone and release scaffolds
+- `#159` Add poll interval context to heartbeat diagnostics
+- `#160` Add heartbeat metric output contract regression
 
 ## Release Execution
 - Use `docs/release/v0.1.42-runbook.md` for preflight, tag/publish, verification, and post-release steps.