Refactor/repair tracking

[kibi2]

Summary

Refactor layout repair tracking used by manual formatting mode.

Changes

• Reorganized buffer-local layout state handling
• Simplified attribute management
• Refactored dirty range tracking
• Clarified responsibilities between repair and rendering logic
• Improved maintainability of internal data structures

Behavior

No user-visible changes are expected.

[codecov]

Codecov Report

❌ Patch coverage is 95.65217% with 24 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
lua/tirenvi/editor/autocmd.lua	86.95%	6 Missing ⚠️
lua/tirenvi/app/pipeline.lua	96.24%	5 Missing ⚠️
lua/tirenvi/io/buf_state.lua	91.42%	3 Missing ⚠️
lua/tirenvi/io/dirty.lua	82.35%	3 Missing ⚠️
lua/tirenvi/core/attrs.lua	94.59%	2 Missing ⚠️
lua/tirenvi/core/attr.lua	91.66%	1 Missing ⚠️
lua/tirenvi/core/blocks.lua	95.23%	1 Missing ⚠️
lua/tirenvi/parser/flat_parser.lua	94.44%	1 Missing ⚠️
lua/tirenvi/util/errors.lua	50.00%	1 Missing ⚠️
lua/tirenvi/util/log.lua	85.71%	1 Missing ⚠️

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