learnings: edit-in-place tmpfile (drop update_learnings tool) (#635)

* learnings: edit-in-place tmpfile (drop update_learnings tool)

learnings now follow the PR-summary file pattern: server seeds
`pullfrog-learnings.md` from `Repo.learnings` at startup, agent reads
it as part of context, may edit in place during the post-run reflection
turn, server reads back at end-of-run and PATCHes if changed.

motivation: `update_learnings` required the agent to pass the FULL
merged list as a string parameter — an output-token tax that grew
linearly with the learnings size, and a constant prompt-context
expansion since the contents were also inlined into the LEARNINGS
section. for repos with mature learnings the prompt was getting
visibly noisy in CI logs.

key changes:
- new `action/utils/learnings.ts` (seed/read helpers + 10k cap)
- `main.ts`: always seed; `persistLearnings` mirrors `persistSummary`
  (success path, error path, exit-signal handler, idempotent guard,
  byte-trim equality skip); forwards `model` for `LearningsRevision.model`
- `LEARNINGS` prompt section now contains only the file path + a
  one-line "read it" instruction (no contents inlined)
- `update_learnings` MCP tool deleted; `action/mcp/learnings.ts` removed
- reflection turn (`buildLearningsReflectionPrompt`) reframed around
  file editing with explicit prune-stale + leave-alone-if-nothing-new
  framing
- `learningsStep` removed from every mode checklist — surface lives only
  in the LEARNINGS prompt section + the reflection turn now

* learnings: harden seed step + refresh stale docs (review feedback)

Three findings from PR review, all implemented:

1. wrap learnings seed in best-effort try/catch (action/main.ts) —
   the always-on seed block ran unconditionally and an unwrapped
   `seedLearningsFile` (mkdir + writeFile) failure (ENOSPC, EACCES,
   hostile sandbox) would unwind into the outer main() catch and flip
   an otherwise-successful run to "❌ Pullfrog failed" before the
   agent even started. asymmetric with `persistLearnings`'s own
   best-effort contract. wrap and log on failure; downstream
   consumers (`persistLearnings`, agent harnesses, `resolveInstructions`)
   already handle `learningsFilePath: undefined` cleanly.

2. refresh wiki/main.md — `resolveInstructions` parameter renamed
   from `learnings` to `learningsFilePath` in this PR; the data-flow
   diagram and the resolver dependency table both still showed the
   pre-refactor signature.

3. drop deleted `learnings.ts` from ROADMAP.md + RESEARCH.md
   "missing MCP tool tests" bullets — `action/mcp/learnings.ts` was
   removed in this PR; the bullets are otherwise still accurate.

mcp/learnings.ts

@@ -1,41 +0,0 @@
-import { type } from "arktype";
-import { apiFetch } from "../utils/apiFetch.ts";
-import type { ToolContext } from "./server.ts";
-import { execute, tool } from "./shared.ts";
-
-const UpdateLearningsParams = type({
-  learnings: type.string.describe(
-    "the FULL merged learnings as a flat bullet list. each line starts with `- `. one discrete, actionable fact per bullet. combine existing bullets from the prompt with your new discoveries. deduplicate — if an existing bullet covers the same fact, update it in place rather than adding a new one. drop bullets that are clearly wrong or no longer relevant to the current codebase. keep the list focused and concise."
-  ),
-});
-
-export function UpdateLearningsTool(ctx: ToolContext) {
-  return tool({
-    name: "update_learnings",
-    description:
-      "persist operational learnings about this repository (setup steps, test commands, key conventions, patterns). ONLY call this when you have high confidence the information is correct and broadly useful for future runs — not for one-off findings or uncertain observations. format: flat bullet list (`- ` per line, one fact per bullet). pass the FULL merged list — combine existing learnings from the prompt with new discoveries. deduplicate, and drop bullets that are clearly wrong or no longer relevant to the current codebase.",
-    parameters: UpdateLearningsParams,
-    execute: execute(async (params) => {
-      const response = await apiFetch({
-        path: `/api/repo/${ctx.repo.owner}/${ctx.repo.name}/learnings`,
-        method: "PATCH",
-        headers: {
-          authorization: `Bearer ${ctx.apiToken}`,
-          "content-type": "application/json",
-        },
-        body: JSON.stringify({
-          learnings: params.learnings,
-          model: ctx.toolState.model,
-        }),
-        signal: AbortSignal.timeout(10_000),
-      });
-
-      if (!response.ok) {
-        const error = await response.text();
-        throw new Error(`failed to update learnings: ${error}`);
-      }
-
-      return { success: true };
-    }),
-  });
-}

mcp/server.ts

@@ -39,7 +39,6 @@ import { GetIssueCommentsTool } from "./issueComments.ts";
 import { GetIssueEventsTool } from "./issueEvents.ts";
 import { IssueInfoTool } from "./issueInfo.ts";
 import { AddLabelsTool } from "./labels.ts";
-import { UpdateLearningsTool } from "./learnings.ts";
 import { SetOutputTool } from "./output.ts";
 import { CreatePullRequestTool, UpdatePullRequestBodyTool } from "./pr.ts";
 import { PullRequestInfoTool } from "./prInfo.ts";
@@ -143,6 +142,21 @@ export interface ToolState {
   // persisted) from redundantly re-running the DB PATCH on the
   // success-then-late-throw path.
   summaryPersistAttempted?: boolean;
+  // absolute path to the rolling repo-level learnings markdown file the
+  // agent reads at startup and may edit at end-of-run. seeded by main.ts
+  // for every run from `Repo.learnings` (empty file when no learnings
+  // exist yet); read back at end-of-run to persist any edits.
+  learningsFilePath?: string;
+  // exact bytes of the seeded learnings file at run start. compared
+  // against the file content at end-of-run to detect "agent never touched
+  // it" — in that case persistLearnings skips the DB PATCH (saving the
+  // identical content would be a no-op write that wastes a LearningsRevision
+  // row and the API round-trip).
+  learningsSeed?: string;
+  // mirror of `summaryPersistAttempted` for the learnings tmpfile — guards
+  // the error-path / exit-signal callers from a redundant second PATCH
+  // after the success path already persisted.
+  learningsPersistAttempted?: boolean;
   output?: string;
   usageEntries: AgentUsage[];
   model?: string | undefined;
@@ -189,8 +203,8 @@ export interface ToolContext {
   tmpdir: string;
   // repo-level OSS flag + account-level billing plan. together they decide
   // whether pullfrog is paying for marginal infra — see isInfraCovered in
-  // utils/runContext.ts. plan gating for things like update_learnings is
-  // enforced server-side via 402, so we pass plan along mostly for future
+  // utils/runContext.ts. plan gating for endpoints like the learnings PATCH
+  // is enforced server-side via 402, so we pass plan along mostly for future
   // use / observability. see wiki/pricing.md.
   oss: boolean;
   plan: AccountPlan;
@@ -288,7 +302,6 @@ function buildOrchestratorTools(ctx: ToolContext, outputSchema?: JsonSchema): To
     DeleteBranchTool(ctx),
     CreatePullRequestTool(ctx),
     UpdatePullRequestBodyTool(ctx),
-    UpdateLearningsTool(ctx),
   ];
 }