feat(duo-workflows): Add Base validator class and program validators

What does this MR do and why?

• Promotes shared validation logic from GitValidator into a declarative Base class using a template method pattern
• Refactors GitValidator to constants-only (all methods now inherited from Base)
• Adds validators for npm, docker, bundle, make, and curl
• Registers all 6 programs in the Registry so pattern approvals work in prod for non-git programs
• This is the user-facing fix: previously, pattern approvals silently failed for non-git programs because only git was registered

Validator architecture

Subclasses configure behavior by declaring constants:

Constant	Purpose
ALLOWED_SUBCOMMANDS	Set of allowed subcommands (nil = simple tool)
ALLOWED_GLOBAL_OPTIONS	Set of allowed pre-subcommand flags
DANGEROUS_FLAGS	Dangerous flag exact matches (defense-in-depth)
DANGEROUS_FLAG_PREFIXES	Dangerous flag prefixes
DANGEROUS_COMPOUND_COMMANDS	Dangerous compound commands like bisect run

Two modes: Subcommand-based (git, npm, docker, bundle) and Simple (make, curl).

New validators summary

Program	Mode	Blocked	Key dangerous flags
npm	Subcommand	exec	--prefix, --script-shell, --userconfig
docker	Subcommand	--	--privileged, --cap-add, --network=host
bundle	Subcommand	--	--gemfile, --shebang
make	Simple	--	-f, -C, --directory
curl	Simple	--	-o, -T, -K, --proxy

References

• Parent epic: Duo should remember command/tool approvals (gitlab-org#20519)
• Resolves: https://gitlab.com/gitlab-org/gitlab/-/work_items/602494+
• Depends on: !240928 (merged) (constrained wildcard matching)
• Pattern approval MR: !233672 (merged)
• Command validators MR: !239862 (merged)

How to set up and validate locally

Run all validator specs:

bin/rspec ee/spec/models/ai/duo_workflows/command_validators/

256 examples covering Base class behavior, GitValidator (unchanged), and all 5 new validators.

MR acceptance checklist

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