Fix the deploy regression strict parsing shipped: --beam-flags no longer works

[GenericJam]

This is a live regression on master. A post-hoc adversarial review of #63 — which I merged without one — found that switching mix mob.deploy to strict parsing broke the documented invocation.

OptionParser will not consume a dash-prefixed argument as a :string value, so:

$ mix mob.deploy --beam-flags "-S 4:4 -A 4" --android
** (Mix) Unknown option(s): --beam-flags, -S 4:4 -A 4

BEAM flags essentially all begin with a dash, so this isn't an edge case — it's every spelling this repo prints, in seven places: the task's own moduledoc, five README recipes, and the "untuned variant" step of both battery benchmarks. The message compounds it by naming --beam-flags, a valid option, as unknown.

Under the old lenient parsing the value was silently dropped and the deploy carried on with whatever mob.exs held — its own bug. Strict parsing turned that into a loud wrong one.

--flag value is now rewritten to --flag=value when the value starts with a dash, for string-valued switches only (doing it for every switch would swallow the flag after a boolean).

Three more from the same review

• The error conflated "unrecognised flag" with "recognised flag, bad value" and threw the value away, so --schedulers abc reported --schedulers as unknown and sent the reader to a help page listing it. mob.new_plugin already had this right; this now matches.
• Positional arguments were still silently dropped.mix mob.deploy --native ABC123 parsed cleanly and deployed to every device — the identical symptom to the bug Refuse unknown options in mob.deploy instead of ignoring them #63 set out to fix, in the same task, left in place by it.
• The four tests Refuse unknown options in mob.deploy instead of ignoring them #63 shipped were all source-text assertions and none ran the parser, so none could have caught any of this. There's now a table test over every invocation the docs print, which fails if a switch is renamed or a documented spelling stops working.

CHANGELOG gains a ### Changed entry for the breaking half: anyone with a wrapper script passing an extra flag goes from working to exit 1, and #63 didn't say so.

2331 tests, credo and format clean.