build(bin): embed sourcemaps in the compiled binary

[TheGreatAxios]

What

Adds --sourcemap to the build:bin Bun compile flags (--compile --minify --sourcemap), so crash stacks from the standalone binary resolve to src/*.ts file-and-line instead of minified frames.

Measurements (darwin arm64, same worktree install, 1168 modules both sides)

	before (HEAD)	after (--sourcemap)
dist/corbits size	74,507,200 B (71.0 MiB)	79,382,752 B (75.7 MiB, +6.5%)
./dist/corbits --help median (5x, /usr/bin/time -p real)	0.75s (0.72/0.73/0.75/0.92/1.54)	0.87s then 0.74s on re-run (0.79/0.82/0.87/1.19/1.99; 0.53/0.57/0.72/0.74/0.80/0.99/1.03)

Startup holds within run-to-run noise (machine variance dominates, ranges overlap); size growth is modest. No rollback trigger met.

Rollback decision (per brief protocol)

--bytecode was tried first (--compile --minify --sourcemap --bytecode) and rolled back: bun build exits 1 with error: "await" can only be used inside an "async" function at src/index.ts:151:18 — Bun bytecode compilation does not accept the entry point's top-level await, and refactoring the entry is out of scope for this change. Kept --sourcemap, dropped --bytecode, re-measured above. No >2x bloat, no codesign breakage (codesign -v passes), no platform build failure with the shipped flags.

Sourcemap packaging

• The map is embedded in the binary: forced-error stacks (e.g. unrecognized flag) resolve to src/config/index.ts:965, src/index.ts:39/117/151 even with no sidecar present.
• Bun additionally emits a stray 13.3 MB dist/corbits.map sidecar next to the binary; it is not needed at runtime (binary runs clean and maps stacks without it).
• Release does not need it: scripts/release.sh compile_bin copies only the binary file into each tarball, never dist/*.map.
• Follow-up landed (720f4a0): scripts/release.sh compile_bin now carries --sourcemap too (--compile --target=… --minify --sourcemap, no --bytecode), so release binaries carry the embedded map. bash -n syntax check passes.

Verification

• bun run check green in the worktree (lint, typecheck, dead-exports, build, projects-dir-guard; 8595 pass, 0 fail).
• Smoke: TUI-less --help launch clean; forced error exits with mapped src/*.ts stack.

Fixes CL-9018

[linear-code]

CL-9018