feat(php-src): add a BSD-licensed crate for php-src derived code

The audit in .ken/php-shim-copying.md judged 14 functions in
shirabe-php-shim (plus php_wordwrap in shirabe-external-packages) to be
line-by-line transcriptions or structural imitations of php-src. PHP's
relicensing to 3-clause BSD makes keeping them legal, but the boundary
between BSD-derived and MIT code was invisible in the source tree.

Moving them into their own crate puts the license into the build
metadata (so NOTICE generation follows the binary), makes a reverse
dependency a compile error, and encodes the origin in the module path,
which mirrors php-src's ext tree. Each function records its origin in a
fixed-format doc comment, and a new php_src_derivation_boundary linter
fails if `php-src` appears in any Rust source outside the crate.

Public paths under shirabe_php_shim:: are unchanged: functions that are
themselves derived are re-exported with `pub use`, and the wrappers that
only validate arguments stay on the MIT side.

This also resolves the duplicate wordwrap implementation.
shirabe_php_shim::wordwrap was todo!(), so SymfonyStyle::block panicked,
while shirabe-external-packages carried its own copy. Both now go
through the single port, verified against real PHP on 13 cases covering
multi-character breaks and cut.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 69 insertions, 0 deletions

diff --git a/LICENSE.md b/LICENSE.md
index fed39f5a..851a1877 100644
--- a/LICENSE.md
+++ b/LICENSE.md
@@ -23,3 +23,72 @@ THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR I
 Shirabe is a port of Composer v2.9.7.
 
 See [composer/LICENSE](composer/LICENSE) for the original Composer license.
+
+## PHP
+
+The `shirabe-php-src` crate (`crates/shirabe-php-src/`) contains Rust port from the
+C implementation of PHP's standard library in [php-src](https://github.com/php/php-src).
+
+### PHP License 4.0 (3-clause BSD)
+
+Applies to everything in `shirabe-php-src` except `src/standard/strnatcmp.rs`.
+
+---
+
+Copyright © 1999–2026, The PHP Group and Contributors.
+Copyright © 1999–2026, Zend Technologies Ltd., a subsidiary company of Perforce Software, Inc.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its
+   contributors may be used to endorse or promote products derived from
+   this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+---
+
+### zlib License
+
+`crates/shirabe-php-src/src/standard/strnatcmp.rs` derives from
+`ext/standard/strnatcmp.c`, which php-src itself carries under the zlib license.
+
+---
+
+strnatcmp.c -- Perform 'natural order' comparisons of strings in C.
+Copyright (C) 2000 by Martin Pool <mbp@humbug.org.au>
+
+This software is provided 'as-is', without any express or implied
+warranty.  In no event will the authors be held liable for any damages
+arising from the use of this software.
+
+Permission is granted to anyone to use this software for any purpose,
+including commercial applications, and to alter it and redistribute it
+freely, subject to the following restrictions:
+
+1. The origin of this software must not be misrepresented; you must not
+   claim that you wrote the original software. If you use this software
+   in a product, an acknowledgment in the product documentation would be
+   appreciated but is not required.
+2. Altered source versions must be plainly marked as such, and must not be
+   misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.
+
+---