Add layout inspection and mutation commands

[pmdci]

Summary

This PR adds the new layout command group to pptx-toolkit for inspecting and mutating slide layout naming metadata in PPTX files.

It covers the full layout-name workflow we researched:

• layout list
• layout remove matching-name
• layout set

The implementation is based on the OOXML distinction between:

• p:cSld/@name
• p:sldLayout/@matchingName

What’s Included

New commands

layout list

Lists slide layouts and shows:

• Layout ID
• Name
• Matching Name
• Master
• Theme
• Used By Slides

Supports filters:

• --layout-id
• --name
• --matching-name
• --theme

layout remove matching-name

Removes p:sldLayout/@matchingName from all matched layouts.

Supports the same filters as layout list.

layout set

Applies directional property assignment across all matched layouts:

pptx-toolkit layout set <source>:<target> input.pptx output.pptx

Supported source forms:

• @name
• @matching-name
• literal string

Supported target properties:

• name
• matching-name

Examples:

pptx-toolkit layout set @name:matching-name input.pptx output.pptx
pptx-toolkit layout set @matching-name:name input.pptx output.pptx
pptx-toolkit layout set "Layout with matchName property":matching-name input.pptx output.pptx --layout-id slideLayout12

Design Notes

Filter model

Layout mutation commands operate on the set of matched layouts.

• no filters = all layouts
• filters narrow the set
• mutations apply per matched layout

set syntax

The layout set parser uses:

• @ on the source side to indicate property reference
• plain property names on the target side

This avoids ambiguity between:

• literal name
• property reference name

Property-to-same-property validation

These forms are rejected early:

@name:name
@matching-name:matching-name

with a clear error, because they would be no-op self-copies.

OOXML-safe mutation strategy

The mutation code does not reserialize full XML documents.

Instead it:

• uses encoding/xml.Decoder only to locate exact start-tag byte ranges
• applies scoped byte-level attribute mutation to those slices only

This avoids OOXML namespace-prefix corruption while still being structured enough to safely target:

• <p:sldLayout ...>
• <p:cSld ...>

Test Fixture

cmd/pptx-toolkit/testdata/test.pptx already contains a dedicated divergent-name layout:

• slideLayout12.xml
• p:cSld/@name = "matchName-test"
• p:sldLayout/@matchingName = "Layout with matchName property"

This fixture is now used for layout inspection and mutation coverage.

Tests

Added/expanded tests for:

• layout XML parsing
• layout set mapping parser
• invalid parser cases
• matchingName removal
• attribute creation/replacement for both layout properties
• literal assignment
• property-to-property copy
• filtered mutation by --layout-id
• copy-from-missing-source behavior
• command filter leakage across repeated executions
• overwrite prompt path now using command-scoped stdin

Refactors / shared behavior

• introduced shared mutation preflight:
  • input validation
  • overwrite prompt
• PromptOverwrite now reads from cmd.InOrStdin() instead of global stdin, making it test-safe
• reused shared layout filter parsing across layout commands
• removed duplicated archive extraction in favor of shared helpers

Documentation

Updated:

• README.md
• .llm/layouts-matching-names.md

to document:

• layout list
• layout remove
• layout set
• mapping syntax
• filter semantics
• implementation notes and testing expectations

Validation

Ran:

go test ./cmd/pptx-toolkit -count=1

and the package test suite passes.