Act IV part 2: The Echo Rite (.) + Waypoints (marks) + The Registers

[StrangeNoob]

Summary

Three medium engine features and their lessons — 27 of 29 lessons shipped. What remains is one final PR: Block Party (Ctrl-v) and The Macro Forge (q/@ + The Archivist boss), which also re-arms the game finale.

New lessons

Act	Lesson	Teaches
IV · 25	The Echo Rite	. — repeats edits and whole insert sessions
IV · 26	Waypoints	m ` ' marks
IV · 27	The Registers	"a–"z named registers

Engine

• Dot-repeat: a Press-level recorder tapes the keys of the change in flight (fresh normal-mode key restarts the tape; pending-state and insert keys extend it; search/cmdline/visual clear it) and commits on an edit or on esc closing an insert. . replays through the real key path with a recursion guard. Not repeatable: u/Ctrl-r, :s, visual ops — like Vim
• Marks: per-buffer map; ` exact jump, ' first-non-blank jump, rows clamp when edits shrink the buffer
• Registers: "x arms a selection consumed by the next yank/paste; yanks always write the unnamed register too. Paste/yank paths refactored around setRegister/takeRegister
• Mark/register name keys bypass allowedKeys like r/f targets; 20 new engine test cases, TDD throughout

Test-harness fix

The solvable-at-par test now skips esc when counting solution keys — the UI has never counted esc (and the test's own comment claimed it didn't). Surfaced by The Echo Rite's A ! esc j . j . solution.

Test plan

• go test ./... green (27 lessons, all solvable at par)
• go vet, gofmt -l clean
• Binary builds; version smoke run

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 7aa79c5f-75ab-462e-95cc-e5cb1f23b3e7

📥 Commits

Reviewing files that changed from the base of the PR and between f6d808e and 3f04b1b.

⛔ Files ignored due to path filters (1)

• docs/lessons.csv is excluded by !**/*.csv

📒 Files selected for processing (14)

• README.md
• assets/lessons/act4-25-the-echo-rite.json
• assets/lessons/act4-26-waypoints.json
• assets/lessons/act4-27-the-registers.json
• docs/LESSON-GAP-ANALYSIS.md
• docs/LESSONS.md
• internal/content/loader_test.go
• internal/content/solvable_test.go
• internal/engine/dot_repeat_test.go
• internal/engine/edit.go
• internal/engine/engine.go
• internal/engine/marks_registers_test.go
• internal/engine/visual.go
• internal/engine/visual_test.go

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/act4-part2

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[StrangeNoob]

CodeRabbit CLI review disposition (4 findings — all valid, all fixed):

• . bypassed allowedKeys (major): fixed with a failing test first — the repeat branch sits above the normal-mode gate, so lessons that never taught . still replayed changes. Now gated like every other command.
• Empty charwise paste crash (minor, but actually a panic): fixed with a failing test first — v y p on an empty line stored an empty charwise yank and drove Cursor.Col to −1, panicking on the next insert. Clamped.
• **Pending() missing m/\``/'/"(minor): fixed** — the HUD now shows all armed pending states, consistent withr/f`.
• README wording (minor): fixed — the still-to-come note now names Block Party and The Macro Forge.