fix(sidebar): compact session tree slot spacing

[bnema]

Summary

• remove the extra gap between tree branch glyphs and slotted session numbers
• keep metadata indentation and mouse click bounds aligned with compact prefix math
• update documented sidebar examples

Verification

• rtk go test ./internal/adapters/uity
• rtk git diff --check

Summary by CodeRabbit

• Documentation

  • Updated the sidebar layout diagram in the README to reflect the latest tree/slot spacing.

• Style

  • Improved tree session rendering to use branch-aware compact prefix spacing, including tighter alignment between tree guide glyphs and slot numbers.

• Tests

  • Added coverage for session-name click bounds when compact slot spacing is enabled.
  • Updated rendering expectations in tree-render tests to match the new compact formatting.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 09ee3c97-dda7-4b06-9550-79646386f1df

📥 Commits

Reviewing files that changed from the base of the PR and between 2e44d99 and 3ead82b.

📒 Files selected for processing (5)

• README.md
• internal/adapters/uity/sidebar_model_test.go
• internal/adapters/uity/sidebar_mouse.go
• internal/adapters/uity/tree_render.go
• internal/adapters/uity/tree_render_test.go

---

📝 Walkthrough

Walkthrough

Introduces compactSlotAfterTreeBranch, a helper that removes the space between tree guide characters (├─, └─) and slot numbers. sessionBodyPrefixWidth gains a branch parameter, renderSession, fitSessionName, and metadataNameIndent are refactored to use it, sessionNameClickBounds caches the branch for hit-testing, and tests plus the README example are updated accordingly.

Changes

Branch-aware compact slot spacing

Layer / File(s)	Summary
Branch-aware rendering helpers and session row layout internal/adapters/uity/tree_render.go	Adds compactSlotAfterTreeBranch(slot, branch) helper; extends sessionBodyPrefixWidth with a branch parameter; renderSession, fitSessionName, and metadataNameIndent each compute the branch once and delegate trimming/indent decisions to the new helper.
Click bounds for compact slots internal/adapters/uity/sidebar_mouse.go, internal/adapters/uity/sidebar_model_test.go	sessionNameClickBounds stores treeBranch(item) in a local variable and passes it to metadataDisplayWidth for the start offset; new test asserts compact-slot click bounds (start=5, end=9) for a last-child slot-2 item.
Updated render test assertions internal/adapters/uity/tree_render_test.go	Four existing test assertions updated from └─ 1 / ├─ 10 to └─1 / ├─10, and one metadata indent reduced by one space to match the new layout.
README sidebar layout diagram README.md	Sidebar layout ASCII example updated to reflect pi-coding-agent placement and revised spacing around the separator and Default/scratch subtree.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• bnema/tmux-session-sidebar#64: Introduces category-first tree_render and tree tests; this PR further refactors the same branch/guide/slot spacing logic and updates the same test expectations.
• bnema/tmux-session-sidebar#68: Modifies tree_render.go rendering paths and tree_render_test.go expectations around tree-guide and current-session marker spacing, overlapping directly with this PR's compact-slot layout changes.
• bnema/tmux-session-sidebar#87: Modifies sessionNameClickBounds-style calculations and sidebar interaction geometry tests, the same code path updated in this PR.

Poem

🐇 Hop, hop — the spaces flee,
└─1 now snuggles tight, you see!
Branch and slot, compact and neat,
No gap between the guide-mark feat.
The rabbit trimmed the whitespace free! ✂️

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title 'fix(sidebar): compact session tree slot spacing' directly and clearly summarizes the main change—removing extra gaps between tree branch glyphs and slot numbers in the sidebar layout.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/sidebar-compact-tree-spacing

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}