feat(moshscript): R8 error convention, shell() verb, TUI /run options

[Preshy]

Follow-up to #18 — completing moshscript implementation (issue #16)

The prior PR was a starting point. This addresses the remaining gaps from PRD 0004:

R8 [P0] — Error convention

CLI verbs now return { ok: false, code } on non-zero exit instead of throwing, so scripts can branch on outcomes without try/catch:

const r = install("claude");
if (!r.ok) say(`install failed (exit ${r.code})`);

Only truly fatal spawn errors (ENOENT) still throw. This prevents a single failing verb from crashing the entire script mid-while (alive) loop.

R6 — shell() verb

Added shell(cmd) to the moshscript vocabulary — runs $SHELL -c <cmd> (blocking, spawnSync with inherited stdio). Returns { ok, code } following the R8 convention. Honors --dry-run.

const test = shell("npm test");
if (!test.ok) notify("tests failed!");

R3 — TUI /run options parity

TUI /run now accepts --max N and --dry-run flags, matching the CLI entrypoint. Both share DEFAULT_MAX=3.

/run deploy.mosh --dry-run --max 5

Tests

8 new tests covering:

• R8 error convention: non-zero exit returns { ok: false }, script continues
• shell() verb: dry-run narration, real execution, error returns, moshscript integration

Docs

• README: documented shell() verb + error handling convention
• TUI /help: updated to show shell() and /run options

Refs #16

[github-actions]

vu1nz Security Review

0 finding(s) in PR #?

No security issues found.

[Preshy]

@ralyodio