refactor(engine): reduce complexity of collect_allowed_tools in src/engine.rs

[github-actions]

What was complex

collect_allowed_tools in src/engine.rs was a ~90-line monolithic function with three distinct concerns packed together, resulting in three nested loops and two inline match arms (estimated cognitive complexity ~20):

1. Collect extension tools — a doubly-nested loop over extension_declarations → copilot_allow_tools with a dedup check
2. Collect MCP server tools — a loop over sorted MCP configs with an inline match to decide whether a config has a backing MCPG server
3. Build bash command list — another doubly-nested loop plus a match arm on front_matter.tools.bash

What changed

Extracted four named helpers, leaving collect_allowed_tools as a 25-line coordinator:

New function	Responsibility
collect_extension_tools	Dedup-collect tool names from all extension declarations
mcp_server_has_backing_server	Pure predicate: does this McpConfig have a container or URL?
add_mcp_server_tools	Append sorted MCP server names to the tool list (skipping duplicates and non-backed servers)
build_bash_command_list	Merge front-matter bash commands with extension-declared bash commands

No public API signatures changed. Behaviour is identical.

Complexity

• Before: ~20 (estimated; below Clippy's default threshold of 25)
• After: ~5 (coordinator only; Clippy clean at all tested thresholds)

Verification

• cargo test — all tests pass
• cargo clippy --all-targets --all-features — zero warnings

Warning

Firewall blocked 1 domain

The following domain was blocked by the firewall during workflow execution:

• spsprodeus21.vssps.visualstudio.com

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "spsprodeus21.vssps.visualstudio.com"

See Network Configuration for more information.

Generated by Cyclomatic Complexity Reducer · 92.8 AIC · ⌖ 12.4 AIC · ⊞ 7.2K · ◷

[jamesadevine]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Merge conflicts resolved in e480c75. The only conflict was in src/engine.rs where main had introduced collect_extension_allowed_tools (with a push_unique_tool helper) doing the same job as our collect_extension_tools. The resolution keeps our add_mcp_server_tools, mcp_server_has_backing_server, and build_bash_command_list helpers and the refactored collect_allowed_tools coordinator, while switching to main's naming (collect_extension_allowed_tools) and removing the duplicate. All tests pass.