Refactor shared pagination/map-extraction paths and isolate server rate-limit helpers

[Copilot]

This change addresses the semantic-clustering refactor findings by reducing repeated helper logic and improving locality of concern. It keeps behavior stable while making shared invariants and extraction paths explicit.

• Rate-limit logic isolation (internal/server)

  • Moved rate-limit parsing/detection helpers out of circuit_breaker.go into rate_limit.go:
    • isRateLimitToolResult
    • isRateLimitText
    • parseRateLimitResetFromText
    • extractRateLimitErrorText
  • Leaves circuit breaker flow focused on state transitions and timing decisions.

• Shared string extraction for map[string]interface{} (internal/strutil, internal/proxy)

  • Added strutil.GetStringFromMap(m, key) and unit tests.
  • Replaced inline string assertions in proxy argument extraction paths:
    • REST-style owner/repo/number extraction
    • collaborator permission arg parsing
    • GraphQL owner/repo variable extraction

• Pagination invariant coupling made explicit

  • Added cross-reference comments between:
    • internal/mcp/pagination.go:paginateAll
    • internal/testutil/mcptest/validator.go:paginate
  • Documents intentional duplication of loop/cursor safety invariants so future edits stay aligned.

// before
owner, _ := argsMap["owner"].(string)
repo, _ := argsMap["repo"].(string)

// after
owner := strutil.GetStringFromMap(argsMap, "owner")
repo := strutil.GetStringFromMap(argsMap, "repo")

[Copilot]

Pull request overview

This PR refactors repeated helper logic without changing behavior, improving locality for server rate-limit handling and shared proxy map-string extraction while documenting pagination invariants.

Changes:

• Moved server-side rate-limit result parsing helpers into internal/server/rate_limit.go.
• Added strutil.GetStringFromMap with unit coverage and adopted it in selected proxy argument extraction paths.
• Added cross-reference comments between production and test pagination helpers.

Show a summary per file

File	Description
internal/server/rate_limit.go	New home for unexported rate-limit parsing/detection helpers.
internal/server/circuit_breaker.go	Removes moved helper implementations and unused imports.
internal/strutil/map.go	Adds shared map string extraction helper.
internal/strutil/map_test.go	Covers helper behavior for present, missing, non-string, and nil map cases.
internal/proxy/proxy.go	Uses shared helper for REST owner/repo/number string extraction.
internal/proxy/graphql.go	Uses shared helper for GraphQL owner/repo variable extraction.
internal/proxy/collaborator_permission.go	Uses shared helper for collaborator permission arguments.
internal/mcp/pagination.go	Documents alignment with test pagination loop-protection invariants.
internal/testutil/mcptest/validator.go	Documents alignment with production pagination loop-protection invariants.

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• Files reviewed: 9/9 changed files
• Comments generated: 0