[Subtask]: Complete ordinary binary-string and charset/collation semantics

### Parent Issue

Primary issues: #25295, #25300, and #25301. Related source-category work: #25299.

Related implementation: #26907.

### Detail of Subtask

Complete ordinary binary-string byte semantics together with charset and collation reporting.

#### Invariant

Binary strings operate on bytes and report the binary charset/collation. Text strings operate on characters and retain their resolved text charset/collation. Equivalent values from different reachable sources must not silently switch domains.

#### Scope

- Length and position: CHAR_LENGTH, LENGTH, BIT_LENGTH, OCTET_LENGTH, LOCATE, INSTR, and position-returning variants.
- Slicing and ordering: SUBSTRING, LEFT, RIGHT, REVERSE, trim functions, case conversion, and byte-preserving transforms.
- Charset/collation consumers: CHARSET, COLLATION, comparison/coercion metadata, and result metadata exposed to SQL clients.
- Inputs: raw literals, _binary literals, BINARY, VARBINARY, BLOB, explicit casts, columns, bare user variables, SQL PREPARE, COM_STMT, mixed rows, typed NULL, and invalid UTF-8 bytes.

#### Acceptance criteria

- [ ] A function matrix records whether each argument is a subject, auxiliary argument, delimiter, or domain selector.
- [ ] Every retained case has a nearest text control and a nearest binary control.
- [ ] Public SQL results are differential-tested against the intended MySQL 8.4 behavior where compatibility is the contract.
- [ ] Mixed-row vectors preserve per-row results without changing the statically declared domain.
- [ ] CHARSET and COLLATION agree with expression metadata, protocol metadata, and materialized column metadata.
- [ ] Invalid UTF-8 is processed as bytes in binary mode and never repaired or truncated implicitly.
- [ ] Focused function tests and public SQL regression tests both cover the matrix.

#### Out of scope

REGEXP source rules and output-width/CTAS sizing are tracked separately.

### Describe implementation you've considered

Classify every argument by semantic role and derive byte/text mode from the owning subject/domain rule. Do not let an auxiliary binary argument accidentally switch the subject's interpretation unless the function contract requires it.

### Additional information

This subtask deliberately includes #25300 even though that parent issue currently carries the deferred label. Creating this subtask does not change that label or the parent's lifecycle state.