fix: Correctness and consistency improvements across core, render, introspect, and CLI

[mhiro2]

Summary

• Harden paths in core / render / introspect / parser / wasm / cli / app that could silently change behavior or panic on malformed input
• Eliminate misclassification and ID collisions in FK / unique validation and stable_id construction caused by identifier case or embedded ., and convert panicking paths in JSON import and
  export into Result
• Align WASM RenderRequest input validation with the other variants, switch SVG output to single-pass XML escaping, and replace magic-string theme detection with a structural field

Changes

• ad24491 : fix(core): case-insensitive FK/unique validation and Result-based import
  • Make validate_fk / column_list_has_prefix / referenced_columns_are_unique case-insensitive so they match the from_columns behavior and stop emitting false-positive
    ForeignKeyNonUniqueTarget on mixed-case names
  • Convert import_schema to return Result<Schema, ImportError> so malformed JSON input produces an error instead of panicking via assert!
  • Assert non-empty stable_id during import to prevent empty IDs from corrupting downstream overlay / diff
• 3fc1804 : fix(render): single-pass XML escape and theme-based light detection
  • Replace the 5-chain .replace() in escape_xml_text with a single-pass char scan, removing 4 intermediate String allocations
  • Add an is_light field to ThemeColors so is_light_theme reads a structural flag instead of comparing against the hardcoded #f7f8fc background
• 63b26e0 : fix(introspect,parser,wasm): harden stable IDs and unify input validation
  • Switch generate_table_id / generate_column_id separators from . to \0 to remove hash collisions when identifiers contain dots
  • Quote .-containing components when building introspect / parser stable_id so that schema="a.b"+table="c" and schema="a"+table="b.c" no longer collapse to the same key, eliminating
    ambiguous lookups in diff / export / graph nodes
  • Route WasmRenderRequest through wasm_input_source() to match the Inspect / Export / Lint / Diff input-validation semantics
• 7f0572b : fix(cli,app): avoid redundant file read and replace .expect() with Result
  • Reuse already-read file contents in read_sniffed_file instead of returning a path variant that triggered a second disk read
  • Replace 5 .expect() calls in the export use case with ok_or_else + AppError so that adding a new ExportFormat variant without updating export_format_uses_graph cannot panic

[github-actions]

Code Metrics Report

	main (cf85e4b)	#84 (7f0e7cd)	+/-
Coverage	94.6%	94.6%	-0.1%
Test Execution Time	1m25s	1m27s	+2s

Details

  |                     | main (cf85e4b) | #84 (7f0e7cd) |  +/-  |
  |---------------------|----------------|---------------|-------|
- | Coverage            |          94.6% |         94.6% | -0.1% |
  |   Files             |             77 |            77 |     0 |
  |   Lines             |          33774 |         33826 |   +52 |
+ |   Covered           |          31981 |         32012 |   +31 |
- | Test Execution Time |          1m25s |         1m27s |   +2s |

Code coverage of files in pull request scope (95.1% → 94.9%)

Files	Coverage	+/-	Status
crates/relune-app/src/request.rs	81.8%	-1.2%	affected
crates/relune-app/src/schema_input.rs	85.0%	-5.6%	modified
crates/relune-app/src/usecases/export.rs	100.0%	+0.4%	modified
crates/relune-cli/src/commands/input.rs	83.7%	-0.3%	modified
crates/relune-core/src/export.rs	98.2%	-1.5%	modified
crates/relune-core/src/lint.rs	95.1%	+0.0%	modified
crates/relune-core/src/model.rs	96.4%	0.0%	modified
crates/relune-introspect/src/common.rs	99.6%	-0.4%	modified
crates/relune-parser-sql/src/lib.rs	93.2%	-0.1%	modified
crates/relune-render-svg/src/edge.rs	95.8%	+0.0%	modified
crates/relune-render-svg/src/group.rs	98.9%	+0.0%	modified
crates/relune-render-svg/src/legend.rs	97.1%	+0.0%	modified
crates/relune-render-svg/src/lib.rs	97.9%	0.0%	modified
crates/relune-render-svg/src/node.rs	91.4%	0.0%	modified
crates/relune-render-theme/src/lib.rs	100.0%	0.0%	modified
crates/relune-render-theme/src/xml_escape.rs	100.0%	0.0%	modified
crates/relune-wasm/src/request.rs	98.8%	+0.8%	modified

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Reported by octocov