cortex import panics with 'byte index is not a char boundary' when file contains UTF-8 chars near 200-byte mark

[nightmare0329]

Bug Report

Version: cortex v0.0.7
Command: cortex import <file>

Description

cortex import panics (process abort) instead of showing a clean error message when the import file contains invalid JSON that includes multi-byte UTF-8 characters near the 200-byte truncation boundary used for error previews.

Steps to Reproduce

# Create a file with a multi-byte character (e-acute, U+00E9) at bytes 199-200:
$ python3 -c "print('x'*199 + chr(0xe9) + 'rest')" > /tmp/bad.txt
# File is 242 bytes total; e-acute spans bytes 199-200

# Import it (JSON parse will fail, triggering the error preview code):
$ cortex import /tmp/bad.txt

Expected Behavior

A clean error message like:

Error: Failed to parse JSON from file: expected value at line 1 column 1

Actual Behavior

thread 'main' panicked at src/cortex-cli/src/import_cmd.rs:76:48
byte index 200 is not a char boundary; it is inside 'e-acute' (bytes 199..201) of `xxx...`
note: run with RUST_BACKTRACE=1 environment variable to display a backtrace
Aborted (core dumped)

Screenshot (real binary output)

Root Cause

In src/cortex-cli/src/import_cmd.rs, the error path computes a preview length using byte count, then slices the string at that byte position — which panics if the byte offset falls inside a multi-byte UTF-8 character:

let preview_len = json_content.len().min(200);  // byte length
let content_preview = &json_content[..preview_len];  // PANICS if mid-char boundary

The fix is to truncate by character count instead of byte count:

let content_preview: String = json_content.chars().take(200).collect();
let truncated = if json_content.chars().count() > 200 { "..." } else { "" };

File: src/cortex-cli/src/import_cmd.rs, lines 75-78

[atlas-cortex]

✅ Validation Summary — Issue #53399

All validation checks passed. 1/17 code rules failed | 1 PENALIZE | 14 LLM instructions active

Confidence Score: 4/5

• All validation checks passed. This submission meets the bounty requirements.

Validation Checks

Check	Status	Detail
Media Evidence	✅ Pass	Evidence found and accessible
Spam Detection	✅ Pass	Score: 21% — no spam signals
Duplicate Detection	✅ Pass	No significant overlap with existing issues
Code Verification	✅ Pass	Bug confirmed in source code (confidence: 100%) — The code in src/cortex-cli/src/import_cmd.rs slices the json_content string
Edit History	✅ Pass	No suspicious edits
LLM Evaluation	✅ Pass	All validation checks passed. 1/17 code rules failed

Validation Pipeline

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    B -->|"✅ Found"| C{"Spam Check"}
    C -->|"✅ Clean"| D{"Duplicate Check"}
    D -->|"✅ Unique"| CV{"Code Verify"}
    CV -->|"✅ Confirmed"| E{"Edit History"}
    E -->|"✅ Normal"| F{"LLM Evaluation"}
    F -->|"✅ Valid"| G["✅ Approved"]
    style G fill:#51cf66,color:#fff

Loading

Raw Evidence

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    "details": "template=0.29 (8 recent issues compared); burst=1.00 (9 issues in 2h window); parity=0.00; overall=0.42 (threshold=0.7); llm_spam=0.00 (The issue provides a highly specific title and a clear description of a Rust panic occurring during string slicing. The steps to reproduce are exceptionally detailed, including a script to generate the exact byte sequence needed to trigger the bug. Expected and actual behaviors are clearly defined, and a screenshot URL is included in the report body. The inclusion of a root cause analysis with specific source code lines further demonstrates the high quality and legitimacy of this submission. There are no indicators of spam or duplication.)"
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  "duplicate": {
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    "topSimilar": [
      {
        "issueNumber": 51195,
        "title": "[BUG] [v0.0.7] `cortex run --dry-run --format json` panics on non-ASCII UTF-8 — byte-slice at char boundary in execution.rs:838",
        "similarity": 0.6431977877235164
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      {
        "issueNumber": 51192,
        "title": "[BUG] [v0.0.7] `cortex run --title \"\" <msg>` panics on non-ASCII UTF-8 — byte-slice at char boundary in execution.rs:126",
        "similarity": 0.6197642892464139
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      {
        "issueNumber": 53262,
        "title": "[BUG] [v0.0.7] cortex-app-server tools/filesystem.rs write_file() metadata preview panics with byte-level slice &content[..500] on multi-byte UTF-8 content",
        "similarity": 0.6107205840179029
      },
      {
        "issueNumber": 53381,
        "title": "[BUG] [v0.0.7] cortex feedback panics displaying non-ASCII feedback entries — byte-index slice at feedback_cmd.rs:329",
        "similarity": 0.6057327831728606
      },
      {
        "issueNumber": 53385,
        "title": "[BUG] [v0.0.7] cortex run panics displaying Unicode message previews — byte-index slice at execution.rs:195,877",
        "similarity": 0.6055162318118072
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    "plausible": true,
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    "reasoning": "The code in `src/cortex-cli/src/import_cmd.rs` slices the `json_content` string using a byte index (`preview_len = json_content.len().min(200)`). In Rust, slicing a string at a byte index that does not fall on a UTF-8 character boundary causes a panic. This perfectly matches the bug report.",
    "codeEvidence": "let preview_len = json_content.len().min(200);\nlet content_preview = &json_content[..preview_len];",
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_{Validated by Atlas • 2026-04-16}