refactor(backend): parse tool options per backend

[risu729]

Summary

• Add a shared BackendOptions reader for raw and platform-scoped backend tool options.
• Add a private typed option wrapper for the unified GitHub/GitLab/Forgejo backend.
• Move GitHub/GitLab/Forgejo option reads and lockfile option collection behind that wrapper while keeping common install/verify helpers on raw ToolVersionOptions.
• Keep HTTP, S3, Aqua, and UBI migrations out of this PR; those are split into separate draft follow-ups.
• Defer Backend::option_specs() metadata changes to a later PR.

Project item

• https://github.com/users/risu729/projects/3/views/1?pane=issue&itemId=185472417
• PR C from project item "Refactor and fix tool option persistence by phase".
• PR A: fix(config): parse core tool options consistently #9742, merged.
• PR B: refactor(config): separate core and backend tool options #9753, merged.
• Draft follow-ups currently split from the original PR C scope:
  • HTTP: refactor(http): parse tool options locally #9870
  • S3: refactor(s3): parse tool options locally #9871
  • Aqua: refactor(aqua): parse tool options locally #9872
  • UBI: refactor(ubi): parse tool options locally #9873

Behavior notes

• This PR is intended to be a refactor and does not change lockfile/manifest persistence classifications.
• The refactor includes two small behavior fixes found while centralizing Git backend option reads:
  • Forgejo now shares the same git install-time option filtering as GitHub/GitLab.
  • no_app is now read through target-aware platform option lookup, so platforms.<target>.no_app works for cross-platform lock resolution.

Review

• Gemini and Greptile AI review suggestions were addressed and their review threads are resolved.
• Manual review focused on preserving existing string/scalar coercion and platform fallback behavior in the Git backend wrapper.

Verification

• cargo fmt --all -- --check
• git diff --check upstream/main...HEAD
• GitHub CI is pending for fda4e0227 after narrowing the PR scope.

This PR was updated by an AI coding assistant.

[gemini-code-assist]

Code Review

This pull request standardizes backend option handling by introducing a BackendOptions wrapper and refactoring the Aqua, GitHub, HTTP, S3, and Ubi backends to use specialized option structs. This change improves code consistency and simplifies option retrieval across different backend implementations. Feedback suggests further improving the BackendOptions utility by adding a platform_bool helper, which would allow the no_app option to be configured on a per-platform basis.

[greptile-apps]

Greptile Summary

This PR centralizes backend tool-option reads behind a new BackendOptions struct (and a GitBackendOptions adapter for GitHub/GitLab/Forgejo), replacing scattered inline opts.get() / lookup_platform_key* calls across github.rs with typed, named methods. Two small behavior fixes are bundled: Forgejo is now included in install_time_option_keys_for_type, and no_app is now resolved through the target-aware platform lookup so platforms.<target>.no_app is honoured during cross-platform lock resolution.

• src/backend/options.rs (new): defines BackendOptions<'a> with str, platform_string, platform_string_for_target, platform_string_for_target_without_base, and platform_bool_for_target; the is_truthy helper accepts \"true\" and \"1\", which is slightly more permissive than the old parse::<bool>() but consistent with how other scalar options are handled.
• src/backend/github.rs: replaces get_api_url, get_filter_bins, and inline option reads with GitBackendOptions methods; unit tests updated to match the new typed signatures.
• src/backend/mod.rs: adds pub(crate) mod options and extends the Forgejo arm in install_time_option_keys_for_type.

Confidence Score: 5/5

Safe to merge — the change is a mechanical refactor that preserves existing option-reading semantics, with two intentional and clearly scoped behavior fixes.

All changed code paths were traced through the underlying ToolVersionOptions accessors. The typed wrappers faithfully delegate to the same lookup functions as before, and the two documented behavior changes are correct and well-tested. No regressions were found.

No files require special attention.

Important Files Changed

Filename	Overview
src/backend/options.rs	New shared BackendOptions wrapper; introduces platform_bool_for_target, is_truthy, and target-aware platform lookup helpers — all correctly implemented
src/backend/github.rs	Migrates option reads to GitBackendOptions wrapper; removes get_api_url/get_filter_bins helpers; fixes Forgejo missing from install-time key filter and enables cross-platform no_app lookup
src/backend/mod.rs	Adds options module and includes Forgejo in install_time_option_keys_for_type alongside GitHub/GitLab

_{Reviews (5): Last reviewed commit: "refactor(backend): split non-git option ..." | Re-trigger Greptile}