fix FlattenResult

feat(iter): add Flatten/FlattenResult, fix Float.String to use decima…

…l format

ErrSeq, OkSeq

refactor(print): replace .type/.debug/.wrap modifiers with format spe…

…c verbs

- Add print_fmt.go with Rust-style format mini-language ({:x}, {:>10.2}, {:+05}, etc.)
- Replace .type with {:T}, .debug with {:?}, .wrap with {:w} verb
- Support alignment (<, >, ^), fill, sign (+, -, space), zero-pad, width, precision
- Support verbs: x/X (hex), o (octal), b (binary), e/E (exponential), ? (#? pretty), T, p, w

feat(option): add Filter, Or, OrElse, IsSomeAnd and mutating methods

- Add Filter for conditional value filtering
- Add Or/OrElse for providing fallback Options
- Add IsSomeAnd to check value against predicate
- Add Insert, GetOrInsert(+With) for mutable value management
- Add Take and Replace for value extraction/swap
- Add OkOr/OkOrElse to convert Option to Result
- Add FromPtr and Ptr for pointer conversions

refactor(encoding): introduce Encode/Decode wrappers and simplify Res…

…ult mapping

- Move encoding functions (Hex, Base64*, XOR, Binary) to dedicated bytes_encdec.go
- Simplify TransformResult to accept fn(T) U instead of fn(T) Result[U]

feat(hash,bytes,string): add HMAC, raw digests, Hex, and Base64 variants

- Add Bytes.Hex() for hex encoding raw bytes
- Refactor bytesHasher → rawHasher to separate digest from hex encoding
- Add *Raw() variants for MD5/SHA1/SHA256/SHA512 returning raw digests
- Add HMACSHA256/HMACSHA512 (hex) and HMACSHA256Raw/HMACSHA512Raw for Bytes and String
- Add Base64Raw, Base64URL, Base64RawURL encode/decode variants to String

feat(pool): preserve submission order in Wait results

Wait now iterates results by task index (0..totalTasks-1) instead of
unordered MapSafe iteration, guaranteeing results match submission order.

feat(print): add {wrap} modifier to Errorf for error chain support

Errorf now supports a {wrap} modifier that simultaneously formats an
error value into the message and wraps it in the returned error,
enabling errors.Is / errors.As to traverse the chain.

Supported forms:
  {.wrap}       — auto-index
  {1.wrap}      — positional
  {name.wrap}   — named
  multiple {wrap} references wrap multiple errors

Add wrappedError type (Unwrap() []error) to errors.go.
Add TestErrorf covering all forms and edge cases.
Add examples/print/ with basic, format, and errorf examples.

perf: optimize deque, heap, map, slice, and string internals

- Deque: extract copyToContiguous helper using copy/clear builtins,
  replace per-element realIndex loops with direct range slices in
  Iter, Contains, and String; bulk-copy in DequeOf, Clone, Reserve,
  ShrinkToFit, MakeContiguous, Slice
- Heap: switch to heapify for bulk Push (O(n) vs O(n log n))
- Map: build MapOrd via direct append instead of Insert in Ordered()
- MapOrd: replace iterator chains with direct loops and pre-allocated
  slices in Map, Safe, Keys, Values
- Slice: remove closure in SubSlice loop condition; two explicit loops
- Slice.Iter: use copy instead of SeqSlice.Collect in SeqSlices.Collect
- String: cache .Std() conversions outside hot loops in Chunks,
  Truncate, writePadding; use rand.N + []byte for default Random
  charset; inline f.Contains/StartsWith/EndsWith as strings.*
- f: cache type conversions outside closures in Contains,
  ContainsAnyChars, StartsWith, EndsWith
- Tests: add TestMapOrdKeys, TestMapOrdToMap, TestMapOrdToSafe