feat(rtff-pdb): RTF and PalmDOC plain-text support (v0.5.0)

rtf.js: a minimal single-pass RTF tokenizer extracting document text
with paragraph structure — groups, control words with signed params,
\\'hh Windows-1252 escapes, \\uN unicode with \\ucN fallback skipping,
known text destinations skipped whole (fonttbl/colortbl/stylesheet/
info/headers/pict/field/...), spec-required ignoring of unknown words.
Format runs are intentionally not converted; RTF is read as styled
text like .txt.

pdb.js: the TEXt/REAd PalmDOC container (PalmDOC, TealDoc) — the PDB
record reader and LZ77 decompressor are shared from mobi.js (both
exported; upstream already carried the TODO for this path). Records
decode as Windows-1252 and feed the plain-text pipeline (paragraph
split, line join, ~150KB sectioning, Part N TOC).

makeBook dispatch: content-based (TEXtREAd magic at offset 60;
'{\\rtf' magic), after MOBI and before the text branch.

Tests: node harness covering store + compressed PalmDOC, RTF paragraphs
/escapes/unicode/hex/destination-skipping, makeBook routing; txt/docx
regression suites pass.

rtf.js

@@ -0,0 +1,149 @@
+// Rich Text Format (.rtf) support: a minimal RTF tokenizer that
+// extracts the document text (with paragraph structure) and hands it to
+// the plain-text pipeline. Format runs (bold/italic/fonts/colors) are
+// intentionally NOT converted — RTF is read here as styled text, the
+// same treatment .txt gets.
+//
+// What is handled: groups, control words with optional signed numeric
+// parameters, \'hh hex escapes (Windows-1252), \uN unicode with \ucN
+// fallback skipping, \par/\line/\tab/page/section breaks, dashes,
+// quotes, spaces, \\ \{ \} escapes, and destination groups that carry
+// no readable text (fonttbl, colortbl, stylesheet, info, pict, object,
+// field/fldinst, generator, list tables, rsid tables, headers/footers,
+// index entries, bookmarks). Unknown control words are ignored (the
+// spec's required behavior); unknown `\*` optional destinations are
+// kept and their text read.
+//
+// Limitations (by design, MVP): tables flatten to plain text, no
+// images, no list numbering, footnotes inline after their reference.
+
+import { makeTextBook } from './text.js'
+
+export const isRTF = async file => {
+    // `{\rtf` magic — content-based, like every makeBook dispatch
+    const head = new Uint8Array(await file.slice(0, 5).arrayBuffer())
+    const magic = String.fromCharCode(...head)
+    return magic === '{\\rtf'
+}
+
+const DESTINATIONS = new Set([
+    'fonttbl', 'colortbl', 'stylesheet', 'info', 'pict', 'object',
+    'thicket', 'field', 'fldinst', 'fldalt', 'generator', 'xmlnstbl',
+    'listtable', 'listoverridetable', 'rsidtbl', 'latentstyles',
+    'datastore', 'themedata', 'colorschememapping', 'pgdsctbl',
+    'header', 'footer', 'headerl', 'headerr', 'headerf',
+    'footerl', 'footerr', 'footerf', 'ftnsep', 'ftnsepc',
+    'aftnsep', 'aftnsepc', 'xe', 'tc', 'bkmkstart', 'bkmkend',
+    'nonshppict', 'mmathPr',
+])
+
+const CP1252_EXTRA = {
+    128: '€', 129: '\uFFFD', 130: '‚', 131: 'ƒ', 132: '„', 133: '…',
+    134: '†', 135: '‡', 136: 'ˆ', 137: '‰', 138: 'Š', 139: '‹',
+    140: 'Œ', 142: 'Ž', 145: '‘', 146: '’', 147: '“', 148: '”',
+    149: '•', 150: '–', 151: '—', 152: '˜', 153: '™', 154: 'š',
+    155: '›', 156: 'œ', 158: 'ž', 159: 'Ÿ',
+}
+
+const decodeByte = code => CP1252_EXTRA[code] ?? String.fromCharCode(code)
+
+const WORD_PARAMS = {
+    par: '\n\n',
+    line: '\n',
+    tab: '\t',
+    page: '\n\n',
+    sect: '\n\n',
+    emdash: '—',
+    endash: '–',
+    emspace: ' ',
+    enspace: ' ',
+    qmspace: ' ',
+    bullet: '•',
+    lquote: '‘',
+    rquote: '’',
+    ldblquote: '“',
+    rdblquote: '”',
+    zwnj: '',
+    zwj: '',
+}
+
+export const rtfToText = input => {
+    const text = typeof input === 'string' ? input : new TextDecoder('windows-1252').decode(input)
+    const n = text.length
+    let out = ''
+    let unicodeSkip = 1
+    // per-group skipping flags; a group skips if it or any ancestor is
+    // a text destination
+    const skipStack = []
+
+    const skipping = () => skipStack.some(Boolean)
+
+    let i = 0
+    while (i < n) {
+        const ch = text[i]
+        if (ch === '\\') {
+            const next = text[i + 1] ?? ''
+            if (next === '\\' || next === '{' || next === '}') {
+                if (!skipping()) out += next
+                i += 2
+                continue
+            }
+            if (next === "'") {
+                const hex = text.slice(i + 2, i + 4)
+                if (!skipping() && /^[0-9a-fA-F]{2}$/.test(hex))
+                    out += decodeByte(parseInt(hex, 16))
+                i += 4
+                continue
+            }
+            if (/[a-zA-Z]/.test(next)) {
+                // control word: letters, then an optional signed integer,
+                // terminated by a (consumed) space or any other character
+                let j = i + 1
+                let word = ''
+                while (j < n && /[a-zA-Z]/.test(text[j])) word += text[j++]
+                let param = null
+                if (/[0-9-]/.test(text[j] ?? '')) {
+                    let digits = ''
+                    if (text[j] === '-') { digits = '-'; j++ }
+                    while (j < n && /[0-9]/.test(text[j])) digits += text[j++]
+                    param = parseInt(digits)
+                }
+                if (text[j] === ' ') j++
+                i = j
+                // process
+                if (word === 'uc' && param != null) {
+                    unicodeSkip = param
+                } else if (word === 'u' && param != null) {
+                    let code = param < 0 ? param + 65536 : param
+                    if (!skipping()) out += String.fromCharCode(code)
+                    // skip the \ucN fallback characters after the escape
+                    for (let k = 0; k < unicodeSkip; k++) {
+                        if (text[i] === ' ') i++
+                        else if (text[i] === '\\' && text[i + 1] === "'") i += 4
+                        else i++
+                    }
+                } else if (DESTINATIONS.has(word)) {
+                    if (skipStack.length) skipStack[skipStack.length - 1] = true
+                } else if (!skipping() && WORD_PARAMS[word]) {
+                    out += WORD_PARAMS[word]
+                }
+                continue
+            }
+            // any other control symbol (\*, \~, \|-…) — ignored
+            i += 2
+            continue
+        }
+        if (ch === '{') { skipStack.push(false); i++; continue }
+        if (ch === '}') { skipStack.pop(); i++; continue }
+        if (ch === '\r' || ch === '\n') { i++; continue }
+        if (!skipping()) out += ch
+        i++
+    }
+    return out
+}
+
+export const makeRTFBook = async file => {
+    const text = rtfToText(new Uint8Array(await file.arrayBuffer()))
+    if (!text.trim()) throw new Error('No extractable text in RTF')
+    return makeTextBook(new File([text], file.name.replace(/\.[^.]+$/, '') + '.txt', { type: 'text/plain' }))
+}