Feat/improve apis - #48

…ipulation

Lets consumers take ownership of the internal Box<str> directly
without going through a String round-trip.

…into_inner to into_parts

Several decode paths (zinc scalar, brio, trio, filter lexer) built a
Str/Uri/Symbol/Ref/XStr from a byte buffer or another owned String by
first borrowing it as &str (sometimes via from_utf8_lossy(..).into_owned(),
which always allocates even when the bytes are already valid UTF-8), even
though the source buffer/String was locally owned and about to be dropped.
Fixed by moving the owned data in directly:

- zinc scalar decoders (str/uri/symbol/reference/id): use
  String::from_utf8(buf) to reuse the already-owned buffer in the common
  valid-UTF8 case, falling back to from_utf8_lossy only on invalid input.
- zinc reference decoder: build via Ref::from(value) + set_dis(dis) instead
  of Ref::make(&str, Option<&str>), avoiding a clone of both the id and dis.
- zinc xstr decoder: use Str::into_inner() to move the parsed value's Box<str>
  straight into XStr::make instead of re-cloning via value.as_str().
- brio decoder: CTRL_STR/CTRL_SYMBOL now move the decoded String directly via
  From<String> instead of Value::from(&str)/Symbol::make(&str); CTRL_REF_STR/
  CTRL_REF_I8 use a new make_ref() helper built on Ref::from()+set_dis();
  CTRL_XSTR and decode_buf_as_xstr pass owned Strings directly.
- trio decoder: Str::from(lines.join("\n")) instead of Str::make(&lines.join(..)).
- filter lexer: Id gained a Box<str>-backed into_inner(); the Rel-symbol path
  uses Symbol::from(id.into_inner()) for a true zero-copy handoff instead of
  going through Display/to_string().

Widened XStr::make() to accept impl Into<Box<str>> for both parameters (was
&str only) so callers can pass an already-owned String/Box<str> without an
extra allocation; existing &str call sites are unaffected since &str already
implements Into<Box<str>>.

Renamed Ref::into_inner/XStr::into_inner to into_parts (they return a tuple
of fields, unlike the single-Box<str> into_inner on Str/Uri/Symbol), added
Ref::from_parts as the inverse constructor, and added tests for
into_parts/from_parts and their round-trip on Ref, plus into_parts on XStr.

Validated with cargo build --all-targets, cargo test --all-targets (331
passed), cargo test --doc (131 passed), and cargo clippy --all-targets (clean).