fix: generated workflows now typecheck, and --all runs

[arnaub]

Two bugs in the workflow generator, both introduced or exposed by #44.

1. Generated classes did not typecheck

#44 added include Ai::Workflow to the template but left the call sig without override..
Sorbet rejects an implementation of an abstract method that does not declare it, so every
regenerated class failed in the consumer:

Method `Ai::Workflows::…#call` implements an abstract method
`Ai::Workflow::ClassMethods#call` but is not declared with `override.`   Sorbet 5051

override. is not decoration — it is what makes Sorbet verify the signature is a legal
implementation of the abstract method.

2. --all never worked

workflow_names = workflow_names   # assigns the nil local to itself
if workflow_names.empty?          # undefined method `empty?' for nil

Ruby binds the local as soon as it parses the assignment, so the right-hand side resolves to
the local being defined, not to #workflow_names. The local is renamed to names.

Only --name worked before, which is why this went unnoticed — the existing generated classes
were all produced one at a time.

Tests

Five examples covering both. Each was verified to fail with its fix reverted. The template
assertions also pin the include and the header forwarding, so a future template edit cannot
quietly drop them again.

Note for anyone extending these specs: generate_all_workflows calls exit 1 when a
workflow fails. Driving the whole method under test tears down the RSpec process and silently
truncates the run — it looked like passing tests with examples missing. Test the pieces instead.
That exit 1 is worth revisiting separately; a generator that kills its caller is hard to use
from anything but a terminal.

Checks

rspec 111 examples, 0 failures. rubocop 40 files, no offenses. srb tc no errors.
Version 0.8.0 → 0.8.1.