[module-resolution] AMPLIFIER_MODULE_<ID> env override honored by inspection commands but not session activation

[bkrabach]

Component: module resolution (amplifier-app-cli, amplifier-foundation — both have Issues disabled, filed here)

Setting AMPLIFIER_MODULE_PROVIDER_ANTHROPIC=/path/to/local/checkout:

Current behavior:

• amplifier module show provider-anthropic correctly displays the override source (code: commands/module.py:65,217,426; source.py:586)
• amplifier run executes the stock installed/cached package with the same env var set

How we know:
Verified via request-param A/B test: both live sessions emitted identical requests with the same env var set; the override path's code demonstrably did not run.

Related issues (same class of problem):

1. [amplifier-app-cli] First-run auto-repair silently reinstalls providers from @main, clobbering pinned/overridden sources #342: auto-repair clobbers pinned installs after install-time gates pass
2. (This issue) env var override honored by inspection, not activation
3. config.providers[].source recorded in mount plans but ignored at activation

The pattern:
Three documented override surfaces, none of which control executed code when a package is already installed. Mount plans and inspection commands record intent, not code identity.

Ask:
Module activation must consult the same override ladder that inspection commands use — or the docs must stop claiming per-session env overrides work.

Related PRs:

• fix: accept canonical reasoning_effort config key (effort remains as alias) amplifier-module-provider-anthropic#76 (canonical reasoning_effort key for anthropic)
• fix: honor reasoning_effort config on normal request path with mount-time validation amplifier-module-provider-openai#55 (canonical reasoning_effort key for openai)
• feat: support full commit SHA refs in bundle git sources (enables reproducible eval) amplifier-foundation#282 (SHA-ref support for reproducible bundle pinning)

Cross-references #342.