[stuffbucket]

Summary

• give production, development worktrees, and packaged test apps stable Tauri identities and isolated data/update behavior
• replace development port scanning with an OS-assigned, persisted port and nonce-bound sidecar readiness protocol
• register the exact loopback capability at runtime, preserve the production localhost:4141 origin, and serialize sidecar restart/failure cleanup
• add the Maximal Test build profile and document the cross-platform profile architecture

Validation

• bun test — 2,381 passed, 0 failed
• bun run check:fast
• cargo check --locked with test externalBin override
• cargo test --locked --lib — 31 passed, 0 failed
• test-profile Tauri debug binary build
• high-effort review with no remaining findings

Notes

• bun run knip still reports the existing unused d3-force and @types/d3-force dependencies; this branch does not modify those dependencies.
• cargo fmt --check still reports the existing broad formatter drift in shell/src-tauri/src/lib.rs; this PR avoids an unrelated whole-file reformat.