[ennerf]

Did an automated survey over the codebase. The commits were checked and incorrect takes were removed. Generated changelog:

Bug fixes and doc corrections for 1.5

Fixes from an agent survey of the runtime, plus typo, link and doc corrections. All commits
were written by Claude and reviewed by the author. Where in doubt, existing behavior is kept
since this is not a major release. Input that worked in 1.4 still parses the same way, except
for the stricter cases listed under behavior changes.

Binary parsing

• Negative lengths throw parse errors instead of exceptions or endless loops.
• Large lengths are checked against the remaining input before allocating memory.
• Fixed an integer overflow when pushing very large limits.
• Buffer sources no longer read past the limits of nested fields.
• Direct sinks and sources accept tagged native addresses (negative values on some Android devices).
• The recursion limit error names ProtoSource instead of ProtoSink.

Repeated fields

• addAll(array, offset, length) respects the offset for objects and enums.
• Adding a repeated enum to itself no longer throws.
• Reused elements no longer keep old values after a shrinking copyFrom.
• addAll and copyFrom no longer reallocate repeated objects that already have enough capacity.

JSON

• Truncated values no longer hang while skipping.
• Base64 without padding is accepted, as the proto3 JSON mapping requires (the built-in source
  threw a NullPointerException). Output is still padded.
• Escaped forward slashes (\/) are accepted in strings and bytes.
• Closing a JSON sink no longer clears the caller's output buffer.
• Invalid characters in numbers throw instead of causing index exceptions or wrong values.
• uint32 and fixed32 accept values up to 2^32-1. Negative values written by older versions
  still parse.

Behavior changes

• int32 values out of range throw instead of being silently truncated.
• Unquoted bytes values are rejected.
• Invalid characters in numbers throw (see above).

Docs

• README fixes (badges, protoc plugin syntax, ProGuard config path), typos and comments.
• Documented the utf8 caching side effect of getSerializedSize(), and growing outputs and
  length-delimited streams.

Verification

• mvn clean package on zulu 8, 25 and 27: 265 tests, 0 failures.
• Protobuf conformance runners 3.20.2 and 3.21.4: 653 successes, 0 failures each.