feat(core): LambdaDelta notebook host — λδ reads and mutates notes

[hyperpolymath]

What this is

The moment λδ first touches a note. Building on the merged L0 kernel (#35), this adds the notebook host — the note-aware builtins registered into a kernel through the seam.

Critically, this preserves the kernel/host split (spec §7): the new code lives in core/src/lambdadelta_host.rs, outside core/src/lambdadelta/. The kernel still knows nothing about notes; an embedder with a different data model would write its own host exactly like this one. Nexia-List is simply the first host.

A note is a letter we send to our future self. — this is the layer where computation starts amplifying the letter.

Bridge — a note becomes data (spec §2)

• note_to_value renders a note as its immutable snapshot map: :id :title :content :attrs :links :backlinks :position :size :prototype :type :created-at :modified-at, with #uuid/#inst tagged ids and instants.
• Total, lossless JSON attribute ↔ λδ value mapping (object keys ↔ keywords). Documented lossy edges on write: keyword/symbol → string, set → array, function → null.

Builtins (spec §4)

Kind	Builtins
Readers (pure)	notes note title content attrs links backlinks position attr search resolve-title agents run-agent
Mutators (!)	create-note! set-title! set-content! (derives [[wiki-links]]) set-attr! remove-attr! move-note! resize-note! link! unlink! delete-note!

Field accessors work on a note map (as self in a formula) or an id, so (content self) reads directly with no round-trip. Mutators are id-based, return the updated note map, and surface errors as values (unknown id → LdError::User).

WASM

WasmNotebook::evalLambdadelta(src) runs notebook-aware λδ in the browser — a thin wrapper over the seam (share the notebook via Rc<RefCell>, install the host, evaluate, reclaim). The pure lambdadeltaEval from L0 stays for host-free evaluation.

Why it matters

This unblocks L1 formulas. The canonical example is a passing test:

(count (words (content (note (resolve-title "Alpha")))))   ; → word count

Verification

• cargo test — 79 green (9 new host tests: formula-over-a-note, search, set-attr!/create-note!/link!/set-content! mutating the real notebook, note-map-as-self, unknown-id-errors; + the kernel & core suites; + seam doc-tests).
• cargo clippy --all-targets -- -D warnings — clean (default and --features wasm).
• cargo fmt --check — clean. cargo check --features wasm — clean. Production code stays panic-free.

Next (per the agreed "1 then 2")

Host bindings first (this PR) → then finish the language core: hygienic defmacro + gensym/macroexpand and multimethods (defmulti/defmethod). Also still deferred: evaluation-context gating (formula pure vs. action may-mutate, spec §5), let/fn destructuring.

Note: estate governance checks are pre-existing estate policy; rust-ci is the relevant product gate.

🤖 Generated with Claude Code

https://claude.ai/code/session_01PAEqVP7Y3bZDhtAaPUTbps

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Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

🔍 Hypatia Security Scan

Findings: 62 issues detected

Severity	Count
🔴 Critical	1
🟠 High	30
🟡 Medium	31

⚠️ Action Required: Critical security issues found!

View findings

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