Merge open contributions: history fix, paste transformer, inline suggestions

[maxlandon]

Bundles the reviewed open contributions onto dev, recommitted as signed commits with original authorship preserved.

Included

• fix(history): return an error from memory.GetLine on out-of-range index (fix(history): return an error from memory.GetLine on out-of-range index #111, @SAY-5, fixes History panic: runtime error: index out of range [1] with length 1 #110)
  The in-memory history source now returns errNegativeIndex/errOutOfRangeIndex instead of panicking, matching the file-backed source's contract. All GetLine callers already treat the error as recoverable.

• Add a bracketed paste transformer hook (Add a bracketed paste transformer hook #113, @M09Ic)
  New exported Shell.PasteTransformer field, letting applications rewrite a normalized paste payload before insertion (e.g. replace it with a [Pasted text #1 +6 lines] placeholder). Empty result inserts nothing. Merged with the SetPasteTransformer method dropped — the bare field matches the SyntaxHighlighter/Completer convention.

• Add inline suggestion display API (Add inline suggestion display API #114, @M09Ic)
  Shell.SetInlineSuggestion/ClearInlineSuggestion/GetInlineSuggestion render application-provided ghost text after the cursor (AI predictions, remote completions, …), gated to line-end with a prefix match. History autosuggest keeps priority.

• feat(inline): commands to accept inline suggestions (new)
  Adds the missing input side for the display API:

  • inline-suggest-accept — accept the whole suggestion.
  • inline-suggest-accept-word — accept the next word.
  • forward-char / vi-forward-char fall back to accepting an inline suggestion at line-end when history autosuggest accepted nothing.
    Acceptance logic lives in internal/display; thin *Shell command wrappers in the root package.

Testing

• go build ./..., go vet ./..., and go test ./... all pass.
• New unit tests in internal/display and end-to-end tests in the root package.

Wiki updated separately: command reference plus new Inline Suggestions and Bracketed Paste pages.

Closes #110. Supersedes #111, #113, #114.

[codecov]

Codecov Report

❌ Patch coverage is 73.26733% with 27 lines in your changes missing coverage. Please review.
✅ Project coverage is 39.04%. Comparing base (088046b) to head (f8270f3).

Files with missing lines	Patch %	Lines
shell.go	54.54%	5 Missing and 5 partials ⚠️
internal/display/engine.go	74.07%	7 Missing ⚠️
internal/display/refresh.go	33.33%	3 Missing and 1 partial ⚠️
emacs.go	81.81%	2 Missing ⚠️
internal/display/inline.go	92.59%	1 Missing and 1 partial ⚠️
vim.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #115      +/-   ##
==========================================
+ Coverage   38.33%   39.04%   +0.71%     
==========================================
  Files          59       60       +1     
  Lines        9516     9606      +90     
==========================================
+ Hits         3648     3751     +103     
+ Misses       5785     5767      -18     
- Partials       83       88       +5     

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