docs: align Whale contributor guidance and templates with Wave Foundation

[LunaStev]

Summary

• Expand CONTRIBUTING.md with Whale-specific setup, component ownership, fork/PR and email-patch workflows, DCO sign-offs, regression expectations, and exact default/all-features verification commands.
• Add MAINTAINERS, COPYRIGHT, NOTICE, and the Contributor Covenant code of conduct, using the published maintainer contact and preserving attribution.
• Adapt Wave's ai.txt to Whale, changing only its project heading and update date while preserving the policy, permission contact, and multilingual notices.
• Add a contributor-focused PR template and replace the three old Markdown report templates with Whale-specific bug, feature, and performance forms. Keep blank reports available and link to the contributor guide instead of a disabled Discussions page.
• Add a short contributor entry point to the README.

Motivation

Make Whale's contribution process consistent with Wave Foundation's existing guidance without copying Wave compiler-specific setup or licensing boundaries into Whale. Contributors should be able to identify the relevant crate, prepare a focused signed-off change, run the appropriate checks, and communicate verification results clearly.

The source guidance is from Wave at ff9f9894, including its contributor guide, maintainer map, copyright/project notices, AI policy, code of conduct, and GitHub templates. Build and test instructions follow Whale's existing Cargo.toml and docs/ci.md.

Component and compatibility impact

Documentation and contribution templates only. The guide distinguishes host support from generated targets, keeps the experimental socket-cli feature explicit, and documents the difference between checking formatting and applying repository-wide formatting.

LICENSE, Rust source, tests, Cargo metadata, CI workflows, funding configuration, and existing CLI documentation are unchanged. No issue is created, edited, assigned, relabeled, or closed by this change, and there are no issue-closing references. No changes are made to the Wave repository.

The branch starts from upstream eeb17f1d, including the recently merged assembler fix, and adds one documentation commit.

Validation

• Verified the five edited/replaced upstream document blobs against their Git blob hashes before building the document snapshot.
• Parsed all three issue forms and their configuration with duplicate-key rejection; checked field IDs, required-field types, options, and existing bug/enhancement label names from the previous templates.
• Checked 24 repository-relative Markdown link destinations against the fetched source tree and the new files, including the README capability anchor.
• Checked Markdown fence balance and shell example syntax with bash -n without executing example Git/Cargo commands.
• git diff --cached --check passed on the exact document snapshot.
• Verified that all 12 uploaded document/template blobs exactly match the locally validated files and that the remote commit diff contains only the intended documentation/template paths.
• Confirmed that the code-of-conduct text differs from Wave only in its maintainer email, and that ai.txt differs only in its project heading and date.

Not run locally: Rust builds/tests/Clippy/rustdoc (Rust is not installed in this editing environment), or interactive GitHub form rendering. No runtime code is changed; existing CI workflows are left intact for the PR checks.

Checklist

• The commit includes a DCO Signed-off-by trailer.
• No runtime regression test is needed for the documentation-only scope; document and template validation is recorded above.
• Contributor-facing changes include matching README links and PR/report templates.
• The final diff contains no source formatting or unrelated refactoring.
• Existing license and third-party attribution notices are preserved.

Prepared with AI assistance at the maintainer's request; validation scope is stated above.