Build Failure: Multiple E0658 (round_char_boundary) and E0004 (non-exhaustive match) in v0.1.8

Environment

• OS: Linux x86_64 (Remote via SSH)
• Rust Toolchain: 1.90.0-nightly (a7a1618e6 2025-07-22) (Also failed on stable 1.88.0)
• Spacebot Version: v0.1.8

Description

The build fails during compilation of the spacebot crate due to two distinct issues. While PR #49 addressed some UTF-8 boundary issues, there are still several occurrences of unstable features and a logic regression in the webchat module.

1. Unstable Library Features (E0658)

The project uses floor_char_boundary and round_char_boundary across multiple files without the necessary #![feature] gates. This breaks builds on stable and even recent nightly toolchains.
Affected files include:

• src/messaging/discord.rs:236
• src/messaging/telegram.rs:732
• src/tools/memory_delete.rs:141
• src/agent/context.rs
• src/tools/search.rs

2. Non-exhaustive Patterns (E0004)

The match statement in src/messaging/webchat.rs is missing several variants of OutboundResponse.
Error:
non-exhaustive patterns: RemoveReaction(_), Ephemeral { .. }, RichMessage { .. }, ScheduledMessage { .. } not covered

Logs

I have attached the full build.txt for a complete trace of all 11 compilation errors.

build.txt

Start by running the spacebot crate build on stable Rust 1.88.0 and compare the output with build.txt. Review the listed floor_char_boundary and round_char_boundary uses, then inspect the OutboundResponse match in src/messaging/webchat.rs. Done means the reported E0658 and E0004 errors, including all 11 compilation errors, are resolved and the crate builds successfully.