fix(build): isolate voip example so the demo build drops cpal/alsa-sys

[jlucaso1]

Problem

Production deploys (Coolify, which builds cargo build --example demo from the Dockerfile) started failing right after the VoIP PR, with:

error: failed to run custom build command for `alsa-sys v0.4.0`
The pkg-config command could not be found.

Root cause

Cargo compiles every root [dev-dependencies] when building any --example, even ones demo.rs never touches. The VoIP PR added cpal (and ringbuf) as a dev-dependency for examples/voip.rs only. So cargo build --example demo dragged in cpal -> alsa-sys, which needs pkg-config plus ALSA dev libraries, both absent in the Alpine/musl builder. cargo chef cook did not catch it because it only cooks the library dependency graph, not the examples.

Installing ALSA in the Dockerfile is not a real fix: the build is a static musl binary on scratch, so alsa-sys would still emit -lasound into the demo link (a binary that does not even use audio), breaking the static link or the runtime on scratch. The right move is for demo to not touch VoIP at all.

Fix

Move examples/voip.rs into its own workspace crate, examples/voip-cli/, which owns cpal/ringbuf, and drop both from the root dev-dependencies. It is a workspace member but not in default-members, so a plain cargo build skips it; run the example with cargo run -p whatsapp-rust-voip-cli.

Result: cargo tree -p whatsapp-rust -i alsa-sys finds nothing anymore, and the demo build no longer compiles the audio stack.

Dependency cleanup (cargo shear)

While here, two genuinely unused dependencies (confirmed manually) are removed:

• postcard in [workspace.dependencies]: referenced by no member (likely a leftover from the refactor(sqlite-storage)!: replace bincode with prost for persisted blobs #911 bincode->prost refactor).
• prost in tests/e2e: unused in the test code.

The remaining cargo shear reports were reviewed and are false positives or intentional, so they are left as-is: serde in waproto (derive injected by build.rs), getrandom (the wasm_js backend), dhat/libsqlite3-sys (feature enablers), and the bench-integration "misplaced" ones (pre-existing, out of scope).

Local validation

• cargo build --example demo compiles without touching cpal/alsa-sys.
• cargo build -p whatsapp-rust-voip-cli compiles.
• cargo build -p e2e-tests --tests compiles without prost.

[coderabbitai]

📝 Walkthrough

Walkthrough

The inline voip example is removed from the root workspace and replaced with a new standalone whatsapp-rust-voip-cli crate under examples/voip-cli/. Related root dev-dependencies (cpal, ringbuf) and a workspace dependency (postcard) are removed. An unused prost dependency is dropped from the e2e test crate.

VoIP CLI Migration

Layer / File(s)	Summary
New voip-cli standalone crate examples/voip-cli/Cargo.toml, Cargo.toml	Introduces the whatsapp-rust-voip-cli crate manifest with package metadata, workspace and local path dependencies (wacore, whatsapp-rust with voip features), and registers it as a workspace member.
Root workspace cleanup Cargo.toml, tests/e2e/Cargo.toml	Removes the [[example]] voip target, cpal and ringbuf dev-dependencies, the postcard workspace dependency, and the prost dep from e2e tests.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main fix: isolating the VoIP example to keep audio deps out of demo builds.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The description directly matches the changes, explaining the VoIP example split, dependency cleanup, and build-failure fix.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/demo-build-drop-cpal

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[github-actions]

📦 Binary size report

Metric	main	PR	Δ
bin size (stripped)	10.10 MiB	10.10 MiB	0
bin .text	8.16 MiB	8.16 MiB	0
bin allocated (text+data+bss)	10.10 MiB	10.10 MiB	0
llvm-lines wacore	644,533	644,533	0
llvm-lines wacore copies	17,879	17,879	0
llvm-lines whatsapp-rust lib	658,431	658,431	0
llvm-lines whatsapp-rust lib copies	20,447	20,447	0
deps crates (Cargo.lock)	465	466	+1 (+0.22%) 🔺

.text per crate

Crate	main	PR	Δ
.text whatsapp_rust	1.49 MiB	1.49 MiB	0
.text wacore	527.65 KiB	527.65 KiB	0
.text wacore_binary	155.84 KiB	155.84 KiB	0
.text wacore_libsignal	165.86 KiB	165.86 KiB	0
.text wacore_appstate	144.24 KiB	144.24 KiB	0
.text wacore_noise	27.71 KiB	27.71 KiB	0
.text waproto	871.99 KiB	871.99 KiB	0
.text whatsapp_rust_sqlite_storage	475.07 KiB	475.07 KiB	0
.text whatsapp_rust_tokio_transport	43.67 KiB	43.67 KiB	0
.text whatsapp_rust_ureq_http_client	8.81 KiB	8.81 KiB	0
.text std	995.60 KiB	995.60 KiB	0
.text other deps	3.29 MiB	3.29 MiB	0

Top movers (cargo-bloat attribution)

Crate	main	PR	Δ
regex_automata	2.90 KiB	1.63 KiB	-1.26 KiB (-43.61%)
prost	370.63 KiB	371.90 KiB	+1.26 KiB (+0.34%)

Baseline: 301f2e030 (latest main run) · Head: cf554bcc7 · Graphs

[cubic-dev-ai]

No issues found across 5 files

_{Re-trigger cubic}

[codspeed-hq]

Merging this PR will not alter performance

✅ 179 untouched benchmarks

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_{Comparing fix/demo-build-drop-cpal (55d94a8) with main (301f2e0)}