chore: add AGENTS.md

[Copilot]

Adds AGENTS.md to document the minimal onboarding steps for agents and developers working in this repo.

Follows guidelines from https://coveord.atlassian.net/wiki/spaces/RD/pages/6647644308/Objective+1+AGENTS.md+Repo+Readiness

Jira: https://coveord.atlassian.net/browse/KIT-5913

[github-actions]

Pull Request Title is not semantic:

�[90m⧗�[39m --- input ---
�[1mAdd AGENTS.md with standardized prerequisites and local dev commands�[22m
�[31m✖�[39m subject may not be empty �[90m[subject-empty]�[39m
�[31m✖�[39m type may not be empty �[90m[type-empty]�[39m

�[1m�[31m✖�[39m found 2 problems, 0 warnings�[22m
ℹ️ Get help: https://github.com/conventional-changelog/commitlint/#what-is-commitlint

[github-actions]

Pull Request Title is not semantic:

�[90m⧗�[39m --- input ---
�[1mAdd AGENTS.md with standardized prerequisites and local dev commands�[22m
�[31m✖�[39m subject may not be empty �[90m[subject-empty]�[39m
�[31m✖�[39m type may not be empty �[90m[type-empty]�[39m

�[1m�[31m✖�[39m found 2 problems, 0 warnings�[22m
ℹ️ Get help: https://github.com/conventional-changelog/commitlint/#what-is-commitlint

[github-actions]

Pull Request Title is not semantic:

�[90m⧗�[39m --- input ---
�[1mdoc: Add AGENTS.md with standardized prerequisites and local dev commands�[22m
�[31m✖�[39m subject must not be sentence-case, start-case, pascal-case, upper-case �[90m[subject-case]�[39m
�[31m✖�[39m type must be one of [build, chore, ci, docs, feat, fix, perf, refactor, revert, style, test] �[90m[type-enum]�[39m

�[1m�[31m✖�[39m found 2 problems, 0 warnings�[22m
ℹ️ Get help: https://github.com/conventional-changelog/commitlint/#what-is-commitlint

[github-actions]

Pull Request Title is not semantic:

�[90m⧗�[39m --- input ---
�[1mdocs: Add AGENTS.md with standardized prerequisites and local dev commands�[22m
�[31m✖�[39m subject must not be sentence-case, start-case, pascal-case, upper-case �[90m[subject-case]�[39m

�[1m�[31m✖�[39m found 1 problems, 0 warnings�[22m
ℹ️ Get help: https://github.com/conventional-changelog/commitlint/#what-is-commitlint