Hide write-oriented prompts and instructions when write tools are filtered

Commencez par lire pkg/inventory/instructions.go et pkg/inventory/prompts.go, puis suivez le filtrage jusqu’à pkg/github/toolset_instructions.go. Reproduisez un inventaire en lecture seule ou exclude-tool et comparez AvailableTools, AvailablePrompts et les instructions générées. Le travail est terminé lorsque les inventaires filtrés n’exposent plus de prompts ni de texte d’instructions laissant entendre que des actions d’écriture non disponibles le sont ; consultez docs/toolsets-and-icons.md pour le comportement documenté.

Problem

Tool filtering can remove write capabilities while prompts and server instructions continue to advertise those same actions. In read-only or explicitly filtered configurations, the server can still expose prompts that instruct the client to create issues, assign Copilot, or open pull requests.

Why now

This server builds instructions and prompts dynamically as part of its safety surface. If filtered capabilities remain documented as available, clients receive contradictory guidance and can plan actions the server has already hidden.

Version under test

• Commit: b1575edfefde09e3cf7c805aea79a92131271659 (origin/main on 2026-03-17)
• Runtime: Go 1.25.7, macOS darwin/arm64

Minimal repro

1. Build an inventory in read-only mode or with write tools excluded.
2. Inspect AvailableTools, AvailablePrompts, and generated server instructions.
3. Compare the filtered tool set with the exposed prompts/instruction text.

Expected behavior

If a write tool is hidden by policy, related prompts and write-oriented instructions should disappear or clearly mark the capability as unavailable.

Actual behavior

Prompt availability is filtered only by toolset/feature flags, and instruction generation does not verify that the referenced write tools survived read-only or exclude-tool filtering.

Code paths

• pkg/inventory/instructions.go
• pkg/inventory/prompts.go
• pkg/github/toolset_instructions.go
• docs/toolsets-and-icons.md

Validation target

Read-only and explicitly filtered inventories should not expose prompts or instruction text that imply unavailable write actions.