[backport] docs: Add CLAUDE.md with project overview and contributor guidance for Claude Code (#1276)

[mergify]

…r Claude Code

Description:

Testing done:

Affected area:

Functional Area
New Functionality	[ ]
CI System	[ ]
CLI Tool	[ ]
Certificate Management	[ ]
Control Plane	[ ]
Demo	[ ]
Documentation	[ ]
Egress	[ ]
Ingress	[ ]
Install	[ ]
Networking	[ ]
Observability	[ ]
Performance	[ ]
SMI Policy	[ ]
Security	[ ]
Sidecar Injection	[ ]
Tests	[ ]
Upgrade	[ ]
Other	[ ]

Please answer the following questions with yes/no.

1. Does this change contain code from or inspired by another project?

   • Did you notify the maintainers and provide attribution?

2. Is this a breaking change?

3. Has documentation corresponding to this change been updated in the fsm-docs repo (if applicable)?

   ---

   This is an automatic backport of pull request docs: Add CLAUDE.md with project overview and contributor guidance for Claude Code #1276 done by Mergify.

[mergify]

❗❗❗
All commits in this PR must be signed off.
Please sign all commits by:

git rebase HEAD~1 --signoff
git push --force-with-lease origin mergify/bp/release/v1.6/pr-1276

[mergify]

Merge Protections

Your pull request matches the following merge protections and will not be merged until they are valid.

🔴 Enforce verified commits

This rule is failing.

Make sure that we have verified commits

• #commits-unverified = 0

🟢 Enforce conventional commit

Wonderful, this rule succeeded.

Make sure that we follow https://www.conventionalcommits.org/en/v1.0.0/

• title ~= ^(\[wip\]|\[backport\]|\[cherry-pick\])?( )?(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert)(?:\(.+\))?:

🟢 Enforce linear history

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Make sure that we have a linear history, no merge commits are allowed

• linear-history