GH-81: feat(github): export Poller.MarkProcessed for host-side cross-poller skip wiring

[alekspetrov]

Summary

Automated PR created by Pilot for task GH-81.

Closes #81

Changes

GitHub Issue #81: feat(github): export Poller.MarkProcessed for host-side cross-poller skip wiring

Context

The github integration Poller keeps a processed-issues set (in-memory map + write-through ProcessedStore.Mark, sdk/integrations/github/poller.go:1043) so findOldestUnprocessedIssue skips already-handled issues. The exported surface currently offers ClearProcessed, IsProcessed, ProcessedCount, and Reset (poller.go:~1510-1547) — but NOT MarkProcessed. The unexported markProcessed exists and is used internally on dispatch.

Host applications need to mark issues processed from OUTSIDE the poller: when a host-side epic executor creates sub-issues and runs them sequentially itself, it must mark those issue numbers in every poller so they are not independently dispatched for parallel execution. The in-tree Pilot poller exposes exactly this as a one-line exported wrapper, and its absence in the SDK poller has caused live duplicate concurrent executions of epic children.

Change

Export MarkProcessed on *Poller in sdk/integrations/github/poller.go, placed next to ClearProcessed:

// MarkProcessed marks an issue as processed (in-memory + persistent store),
// so the poll cycle will not dispatch it. Used by hosts that create and
// execute sub-issues themselves and must prevent independent re-dispatch.
func (p *Poller) MarkProcessed(number int) {
	p.markProcessed(number)
}

Semantics identical to the internal path: in-memory map insert + write-through processedStore.Mark("github", p.repoKey(), strconv.Itoa(number)) when a store is configured. No other behavior changes.

Acceptance Criteria

• Poller.MarkProcessed(number int) exported, delegating to the existing unexported markProcessed.
• After MarkProcessed(n): IsProcessed(n) == true, and a poll cycle does not dispatch issue n.
• With a configured ProcessedStore, Mark is called with the poller's own repo key (verify via a fake store in a table-driven test).
• ClearProcessed(n) after MarkProcessed(n) restores dispatchability (round-trip test).
• No changes to any other exported API; go test ./... green.

Out of Scope

• Any change to ProcessedStore interface or core.PollerDeps.
• Host-side wiring (lands in the consuming application).

Planned Steps (execute all in sequence)

• Step 1: feat(github): export Poller.MarkProcessed for host-side cross-poller skip wiring — In sdk/integrations/github/poller.go, add an exported one-line wrapper func (p *Poller) MarkProcessed(number int) { p.markProcessed(number) } placed adjacent to ClearProcessed (~line 1510). The wrapper delegates to the existing unexported markProcessed, preserving the in-memory map insert + write-through processedStore.Mark("github", p.repoKey(), strconv.Itoa(number)) semantics with no behavior change. Add table-driven tests in sdk/integrations/github/poller_test.go (or the nearest existing processed-set test file) covering: (a) MarkProcessed(n) -> IsProcessed(n) == true; (b) with a fake ProcessedStore, Mark is invoked exactly once with source "github", the poller's own repoKey(), and strconv.Itoa(n); (c) a poll cycle after MarkProcessed(n) does not dispatch n (assert via findOldestUnprocessedIssue skipping it); (d) round-trip: ClearProcessed(n) after MarkProcessed(n) restores dispatchability. Verify no other exported API changes (re-run TestPublicAPILocked if the github package has an equivalent guard; otherwise diff exported decls manually) and confirm go test -race ./... and go vet ./... are green.