feat: add provider-aware summary error handling

[peyton-alt]

Summary

• normalize summary-provider failures across Codex, Gemini CLI, Copilot CLI, Cursor, and Pi
• preserve decoded provider errors and cancellation/deadline causes through streaming and explain rendering
• classify authentication, rate-limit, configuration, and missing-CLI failures into actionable guidance
• keep automatic-summary failure logs privacy-safe by recording only structured metadata

Stack

This PR is stacked on #1230, which is stacked on #964. Merge in that order.

It supersedes the older implementation in #1005 and carries forward the intent reviewed in Entire trail 193 without adding that old branch directly to the active stack.

Verification

• mise run check — lint, race-enabled unit/integration suite, Vogon 59/59, Roger-Roger 4/4
• race-only fallback-timeout regression repeated 50 times
• isolated black-box failures: missing CLI, 401, 429, 400/404, generic exit, empty output, worker 404, partial timeout, and Pi auth/empty output
• real Codex native streaming and compatibility fallback both completed successfully

Native Pi calls were attempted but could not complete because the available OpenAI credential was quota-limited and the Google credential was invalid; Pi's deterministic error-path coverage passes.

---

Note

Medium Risk
Touches core summary generation, streaming fallback, and user-visible explain errors across multiple providers; behavior changes are well-tested but affect failure UX and error precedence on timeouts/cancellation.

Overview
Summary generation failures from external CLIs are now normalized into a shared TextGenerationError with provider identity, failure kind (auth, rate limit, config, missing CLI), message, stderr, exit code, and stdout byte counts.

RunIsolatedTextGeneratorCLI takes a provider enum instead of separate binary/display strings, returns (string, error) only, and builds typed errors via classifyTextGenerationFailure (contextual HTTP status patterns, Gemini auth phrase). Codex, Copilot, Cursor, Gemini, and Pi GenerateText paths wrap those errors instead of assembling their own envelopes. Pi gains injectable CommandRunner for tests.

StreamingGeneratorTemplate uses the same newTextGenerationError shape, classifies start/exit failures, and refines precedence: specific decoded provider errors beat concurrent deadlines; unknown provider/parser failures still join context cancellation/deadline with subprocess causes.

Explain and ensureSummaryProviderPresent surface missing or misconfigured providers as typed failures with user-facing labels via formatProviderSummaryError. Auto-summary condensation logs only structured metadata (no stderr/message content). Tests expand across isolated CLI helpers, streaming template subprocess fakes, and provider error matrices.

^{Reviewed by Cursor Bugbot for commit 4ee08c3. Configure here.}

[Copilot]

Pull request overview

This PR standardizes summary-generation failures across multiple providers by introducing a richer, provider-aware TextGenerationError shape, updating both non-streaming and streaming execution paths to preserve meaningful causes, and improving entire explain --generate rendering while keeping auto-summary logs privacy-safe.

Changes:

• Introduces provider/kind-aware TextGenerationError classification in the shared isolated CLI runner and streaming template, and updates provider agents to use it.
• Updates explain --generate to render provider-typed failures (including “missing CLI”) consistently and preserve unwrap chains for cancellation/deadline behavior.
• Adjusts condensation auto-summary logging to record only structured metadata and expands tests across error matrices and subprocess fakes.

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
cmd/entire/cli/strategy/manual_commit_condensation.go	Switches auto-summary failure logging to structured, privacy-safe attrs.
cmd/entire/cli/strategy/manual_commit_condensation_test.go	Adds a regression test ensuring provider content is excluded from failure log attrs.
cmd/entire/cli/explain.go	Adds provider-typed summary error formatting/rendering and preserves cause chains via a formatted wrapper.
cmd/entire/cli/explain_test.go	Expands tests to cover non-Claude provider matrices, precedence, and cause preservation.
cmd/entire/cli/explain_summary_provider.go	Returns typed TextGenerationError for “configured provider missing CLI” instead of a generic error.
cmd/entire/cli/explain_summary_provider_test.go	Adds coverage verifying missing CLI errors are typed.
cmd/entire/cli/agent/text_generator_cli.go	Refactors isolated CLI runner to be provider-aware, returning a typed error with classification and metadata.
cmd/entire/cli/agent/text_generator_cli_test.go	Reworks tests around a helper subprocess, adds classification/precedence assertions, and validates generator wrapping behavior.
cmd/entire/cli/agent/streaming_template.go	Aligns streaming error handling with the same typed provider-aware error shape and precedence rules.
cmd/entire/cli/agent/streaming_template_test.go	Rebuilds tests to use a subprocess helper and validates classification/precedence and error-chain properties.
cmd/entire/cli/agent/pi/pi.go	Adds injectable CommandRunner on PiAgent.
cmd/entire/cli/agent/pi/models.go	Updates list-models path to the new isolated runner signature.
cmd/entire/cli/agent/pi/generate.go	Updates Pi generation path to use provider-aware isolated runner with injected runner support.
cmd/entire/cli/agent/pi/generate_test.go	Adds Pi error-path tests (missing CLI/auth/empty output) validating classification and wrapper counts.
cmd/entire/cli/agent/hook_command_windows_exec_test.go	Minor constant rename usage for Windows-only execution test gating.
cmd/entire/cli/agent/hook_command_test.go	Aligns OS constant usage with production hook wrapper selection logic.
cmd/entire/cli/agent/geminicli/generate.go	Migrates Gemini generator to the new isolated runner return shape and relies on typed error wrapping.
cmd/entire/cli/agent/cursor/generate.go	Migrates Cursor generator to the new isolated runner return shape and relies on typed error wrapping.
cmd/entire/cli/agent/copilotcli/generate.go	Migrates Copilot CLI generator to the new isolated runner return shape and relies on typed error wrapping.
cmd/entire/cli/agent/codex/generate.go	Migrates Codex generator to the new isolated runner return shape and relies on typed error wrapping.